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[Music]

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to yure 2 with three Jango talks the

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first one is called Jango rest and Open

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PI a gentle

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introduction and it's by Paul

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waer um I hate glasses uh Paul is a six

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foot tall ape descendant and nobody is

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currently trying to bypass through his

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home he works for an open source company

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and in spare time he maintains websites

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rides electric motorbike teaches Iris

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set dancing plays the piano reads

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Science Fiction and Fantasy 3D prints

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and collects esoteric Hobbies I wish I

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had that

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much welcome to your talk thank you

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thank you and greetings from Nal country

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where I come from um I have been

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programming for a fair while uh which is

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why I use boring uh default uh Libra

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office impress templates uh and

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currently I work at a small uh open

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source company that few people have

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heard of uh working on an API that only

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our customers can actually access uh so

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instead I thought I'd do my demo on one

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of my other Hobbies uh which is mixing

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electronic music um and I published them

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on uh my website uh each mix has a list

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of tracks uh is distributed through a

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number of files and can be linked to one

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or more Styles so I want to provide um

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an API for that uh so I'm going to

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assume that you know mostly about Python

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and Django uh and on the other hand if

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you already know a lot about Django rest

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framework uh open API uh and using that

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um the exits are there um I'll be

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leading the way um so let's talk a bit

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about what apis actually are uh a good

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talk on Friday I think by Ash said that

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uh rest is a really overused term and it

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probably doesn't mean what it used to

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mean basically all we're talking about

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here is an interface for programs to

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read data from something you publish

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usually a website um so that means that

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the data is going to come not in a nice

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template

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um the camera crew really wants me to

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stay in one place so I'm going to have

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to fight my instinct to point all over

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the place um so the um

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uh the programs are going to read this

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uh output so it's going to be in a

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standard format uh it's not going to be

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rendered nicely in HTML and things like

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that uh and in Django we have standard

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methods of doing this you've got models

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which store the data uh and then those

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views um get referenced through the URL

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grab the data from the models and

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present it in templates D Jango rest

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frame work works very similarly the only

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real change is that we use serializers

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instead of templates uh and I'll cover

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those in a sec so for my website uh if

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you go to mixers uh you get the list of

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all the mixers and if you go to mix

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number one you get the first mix that I

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produced uh and if you go to

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mixstyle

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SLR then you get all of mixes just of

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that style and we want to Pro provide uh

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the mixers API um which lists which has

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sort of very similar things we have a

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list of mixes and we want to publish um

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details on mix one and so we've all

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written view code like this um grabbing

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all of the mixes the latest news the

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last data mix was completed um and

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render that using a template uh likewise

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um

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mix details uh this is where we get a

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bit complicated and we might want to

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change this at some point because uh

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mixers have a number but they can also

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have multiple Parts I some mixers I did

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two parts on the same day uh some mixes

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I have gone back and reworked and so the

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rework is mix

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1.2 um so we've all written view code a

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bit like this now one of the things that

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I really love about Jango Jango and I

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think more Frameworks out there should

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embrace this principle is don't repeat

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yourself but we seem to have written

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that code a lot for view list views and

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detail views and search views and you

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know create views all of those sort of

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things it's the same code over and over

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again and so normally when we go through

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this Evolution uh we get to we start

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writing our own views and then we find

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out that someone's done this before so

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we get generic views and then we we hit

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the limitations on generic views really

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quickly uh and usually we get told yeah

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actually you have to go back and

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reimplement all of your

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stuff so Jango rest framework has uh an

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idea called view sets um I'm going to

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talk about that uh as one of the

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fundamental things to take away from

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Dango rest framework what do they look

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like like so here's uh a really basic

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view set that I wrote um for mixers um

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we're using the readon model view set so

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that um will introspect my model I just

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tell it the query set that I want to

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look at and then the serializer class

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that is going to take that data and

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present it to the outside

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world that's it that has all the inbuilt

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code to handle the list View and the

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detail view it's also got all the

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inbuilt code to say if someone tries to

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say create a new mix and this is a

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readon model view set um then they get a

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405 method not allowed also really nice

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if I want to change uh how that mix set

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is um presents its detail so instead of

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the um number I want to present a much

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more readable slide

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all I have to do is just add the lookup

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field Slug and that will know to get the

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right field out of the mix qu the query

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set when it's looking for that detail

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view all the 404s everything handled

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just fine that's really really

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compact so let's talk about that

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serializer that I was kind of glossing

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over before

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um D Jango uh we have template to Output

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data from the internal representation

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out to the outside world and we've got

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forms to take data from the outside

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world and turn take it into our Jango

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model template so for um Django rest

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framework the serializer does both of

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those functions what does a serializer

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look like well here's the mixed

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serializer and we give it we based on

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the model serializer class uh we give it

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the model and we tell it which fields we

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want to

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Output

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um the complication here remember I

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talked about that number and part those

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two Fields aren't really completely

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independent we'd like to present them as

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one thing um there's a couple of ways we

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can do that one is we can take the

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describe the the field a bit more and we

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can use a serializer method

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field um that looks for a get uncore

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field name method in the serializer uh

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and then outputs the number or the part

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if it has a part but that's only read

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only we can't um put data back into that

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so instead what we might do if we want

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to uh input at some point I might

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actually like to have an external

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program create these things for me

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um we Define our own field and the all

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the field really needs to do is do two

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things one is take the internal view the

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internal mix and um output the

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representation we want the external

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world to see the other is uh taking the

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external representation and using the

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magic of regexes and named Rix

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um Fields uh uh and group dict uh we

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just return a dictionary um if we got a

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match uh and that dictionary contains

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the number and the part Fields uh and if

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we didn't match then there's some kind

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of validation error so raise that and

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that's all we need for our mixed number

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field we just make sure that we

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reference mix number in the fields list

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um as opposed to the number and the

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number and part Fields like likewise uh

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we can have a track

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serializer um that just is based on the

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track and outputs the number and artist

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and title and we can include that track

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serializer as a field in our mix

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serializer We Tell It many equals true

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which means that that is going to Output

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a list of fields not just a single field

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and we give it the source which will be

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the foreign key relationship from the

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mix if you're you're doing uh in the you

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know Django uh you've got Django shell

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uh and you do mix. track set that will

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give you the query set of tracks within

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the mix um so that's the that's the

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source we're looking at that's all I

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need to do to include all of that data

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as a su list in my actual

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mix that is really convenient I have to

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say Okay so

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um we've got our mix view set um how do

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we actually present that to the outside

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world so in Django uh we would uh create

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the URLs list uh as a list of paths um

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which link the actual um text fragment

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to the view method or class um and that

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looks something like this so we have the

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index view um based on the blank path um

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linking the to the views. index function

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uh and they're named so we can refer to

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them in tests uh likewise we have two

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linking to the mixed page depending on

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whether we got a number or a number.

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part in D Jango rest framework this

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works slightly differently um we it has

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the concept of a router and routers

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gather view sets and they can enumerate

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the um methods provided by that view set

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and turn them into

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URLs that in your code will look

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something like this so we import the

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routers uh we create a simple router and

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we register against the mix path

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fragment uh we register the mix view set

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and then we just include that router.

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URLs in our API path

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um because I've been doing this a while

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and I don't do live demos very well um

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this is the copy and paste of my live

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demo um and that uh query basically so

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we mapped mix and then it looked at yes

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there's actually a part after this so

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this must be a detail view that's the

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slug that we gave it

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it takes the slug puts it into the um

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query set finds a single item so we

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didn't get a

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404 um gets that item feeds it through

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the serializer output outputs

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that um the so the view set and the

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router has known how to map all of that

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path information back into uh an actual

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query and we haven't had to spell that

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out at all uh so that works for the the

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list view works for the detail view we

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can also add extra actions so here we

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use the action decorator um and we tell

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it at detail equals false we're going to

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return a just the mixes and a random

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order I don't know it's a demo um and

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here we need to do a little bit more

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work uh this is not um a simple thing um

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in terms you know compared to just using

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the default list output but all this

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this is what your standard this is sort

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of the list or detail um methods would

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look like this so U they start with the

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request um we're going to return a

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response object we get our serializer we

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give it the query set that we want it to

274
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serialize We Tell It many equals true so

275
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that it it will output a list and then

276
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we ask for the data out of that

277
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serializer

278
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the response then feeds that through the

279
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renderer to Output Jason or yaml or CSV

280
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or whatever um and so out out of that um

281
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comes a chunk of

282
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Json but most

283
00:14:48,519 --> 00:14:55,800
importantly when I add that I don't have

284
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to change the router or the URLs at all

285
00:14:55,800 --> 00:14:59,639
the router automatically introspects

286
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finds that action

287
00:14:59,639 --> 00:15:05,720
adds that to the set of paths that it

288
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recognizes that is don't repeat

289
00:15:05,720 --> 00:15:10,880
yourself okay so where was I up to we

290
00:15:08,079 --> 00:15:13,320
need to talk a bit about uh

291
00:15:10,880 --> 00:15:15,360
authentication um this is a little bit

292
00:15:13,320 --> 00:15:18,440
more complicated these are the things

293
00:15:15,360 --> 00:15:22,519
that I found myself stumbling over a

294
00:15:18,440 --> 00:15:25,600
little bit um but if we wanted something

295
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where I could um write a program to add

296
00:15:25,600 --> 00:15:33,839
new mixes um but everyone else just sees

297
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standard view um we there are two phases

298
00:15:33,839 --> 00:15:39,639
to Jango rest Frameworks sort of

299
00:15:36,639 --> 00:15:41,519
authentication permission system one is

300
00:15:39,639 --> 00:15:44,360
the authentication so it looks at the

301
00:15:41,519 --> 00:15:45,800
request you've made sees if there's any

302
00:15:44,360 --> 00:15:49,480
uh information in there that

303
00:15:45,800 --> 00:15:52,959
authenticates you grabs that tries um

304
00:15:49,480 --> 00:15:56,600
tries to see if it's valid uh and then

305
00:15:52,959 --> 00:15:59,120
if it is one of those authentication

306
00:15:56,600 --> 00:16:01,880
authentication classes will return and

307
00:15:59,120 --> 00:16:04,600
your request object will now have an or

308
00:16:01,880 --> 00:16:06,240
property which has the authentication

309
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information in

310
00:16:06,240 --> 00:16:14,880
it um the permission

311
00:16:10,079 --> 00:16:17,279
class uh then checks which of the

312
00:16:14,880 --> 00:16:20,279
whether you're actually allowed to do

313
00:16:17,279 --> 00:16:22,319
the request that you have asked to do so

314
00:16:20,279 --> 00:16:25,120
here I'm using the standard is

315
00:16:22,319 --> 00:16:28,319
authenticator or if is authenticated or

316
00:16:25,120 --> 00:16:31,199
readon permission um does kind of what

317
00:16:28,319 --> 00:16:33,560
it says on the tin um there's only one

318
00:16:31,199 --> 00:16:35,839
authenticated user on my website and

319
00:16:33,560 --> 00:16:38,519
that's me so that's really simple I

320
00:16:35,839 --> 00:16:43,279
didn't have to work out who uh who else

321
00:16:38,519 --> 00:16:45,920
was allowed to see uh or create mixes um

322
00:16:43,279 --> 00:16:48,199
OB if you are if you need more

323
00:16:45,920 --> 00:16:51,639
information uh in your permission class

324
00:16:48,199 --> 00:16:54,880
about exactly who is allow allowed to um

325
00:16:51,639 --> 00:16:58,079
access exactly what you'd modify uh your

326
00:16:54,880 --> 00:17:00,040
own permission class the trick with

327
00:16:58,079 --> 00:17:02,519
permission class is where where the

328
00:17:00,040 --> 00:17:06,079
authentication class the first one of

329
00:17:02,519 --> 00:17:09,360
those to authenticate wins and it says

330
00:17:06,079 --> 00:17:13,839
yes authenticated uh the permission

331
00:17:09,360 --> 00:17:16,919
class um if the if any one of those

332
00:17:13,839 --> 00:17:20,640
returns false then you're

333
00:17:16,919 --> 00:17:24,120
denied uh you can actually a and and

334
00:17:20,640 --> 00:17:26,640
these together which is pretty neat U so

335
00:17:24,120 --> 00:17:30,280
you can make a combination of permission

336
00:17:26,640 --> 00:17:33,120
classes um but the idea with your

337
00:17:30,280 --> 00:17:36,720
permission class is that if there's if

338
00:17:33,120 --> 00:17:40,320
it if it doesn't say

339
00:17:36,720 --> 00:17:43,320
yes then and it says no Then whichever

340
00:17:40,320 --> 00:17:44,360
one of those uh says no will win and

341
00:17:43,320 --> 00:17:49,480
you'll get

342
00:17:44,360 --> 00:17:51,880
denied okay testing um there's not a lot

343
00:17:49,480 --> 00:17:55,039
to say about testing everyone here is

344
00:17:51,880 --> 00:17:59,679
obviously uh doing all of their tests on

345
00:17:55,039 --> 00:18:01,640
their Dango um systems so the only real

346
00:17:59,679 --> 00:18:04,919
thing that I want yes I lots of heads

347
00:18:01,640 --> 00:18:07,080
nodding thumbs up yeah agreed um so the

348
00:18:04,919 --> 00:18:12,200
only thing I really want to point out

349
00:18:07,080 --> 00:18:15,720
here is uh the reverse name um that has

350
00:18:12,200 --> 00:18:19,559
been created by the router out of the

351
00:18:15,720 --> 00:18:23,360
path fragment that we gave it um or a

352
00:18:19,559 --> 00:18:27,720
base name if we supplied that and the

353
00:18:23,360 --> 00:18:30,799
view name so list handles lists details

354
00:18:27,720 --> 00:18:36,679
handles detailed View use

355
00:18:30,799 --> 00:18:42,240
um when we um post to if we want to

356
00:18:36,679 --> 00:18:46,480
create uh a mix We post to the mix uh

357
00:18:42,240 --> 00:18:49,640
list View and so that's kind of uh how

358
00:18:46,480 --> 00:18:53,320
that it's not named mixor create at that

359
00:18:49,640 --> 00:18:56,840
point um but those names come for free

360
00:18:53,320 --> 00:18:58,960
again we don't repeat ourselves that's

361
00:18:56,840 --> 00:19:04,400
nice as well

362
00:18:58,960 --> 00:19:08,080
okay so open API uh what is it um it

363
00:19:04,400 --> 00:19:10,720
used to be called Swagger um and it's

364
00:19:08,080 --> 00:19:14,919
basically in the same way that apis

365
00:19:10,720 --> 00:19:19,280
allow programs to talk to your

366
00:19:14,919 --> 00:19:22,280
um website and get information um the

367
00:19:19,280 --> 00:19:25,240
open API standard allows the program

368
00:19:22,280 --> 00:19:27,760
talking to you to see what that data is

369
00:19:25,240 --> 00:19:31,200
going to look like what queries it can

370
00:19:27,760 --> 00:19:34,720
um give make on your you know what what

371
00:19:31,200 --> 00:19:38,120
creery parameters what the uh example

372
00:19:34,720 --> 00:19:41,720
data that you might Supply looks like uh

373
00:19:38,120 --> 00:19:45,559
that often is supplied as yaml uh here's

374
00:19:41,720 --> 00:19:48,799
an example um and it basically lists the

375
00:19:45,559 --> 00:19:51,520
paths uh combined with a

376
00:19:48,799 --> 00:19:56,240
description um which you might

377
00:19:51,520 --> 00:20:00,320
recognize um from the model that we

378
00:19:56,240 --> 00:20:03,320
um uh from what the model we supplied

379
00:20:00,320 --> 00:20:04,799
and then it lists content it lists a

380
00:20:03,320 --> 00:20:06,080
whole bunch of other stuff don't worry

381
00:20:04,799 --> 00:20:10,360
too much about

382
00:20:06,080 --> 00:20:12,720
that uh so I'm using the uh package drf

383
00:20:10,360 --> 00:20:15,799
spectacular um there used to be an old

384
00:20:12,720 --> 00:20:20,039
one drf YK uh they only coped with open

385
00:20:15,799 --> 00:20:22,960
API 2 uh spectacular is the three

386
00:20:20,039 --> 00:20:25,919
variant um that you need a little bit

387
00:20:22,960 --> 00:20:28,720
more setup you um install it and then

388
00:20:25,919 --> 00:20:32,080
you need to plug in um the spectacular

389
00:20:28,720 --> 00:20:34,360
settings in your settings Pi file uh the

390
00:20:32,080 --> 00:20:37,840
main obviously fill in your title and

391
00:20:34,360 --> 00:20:41,000
description uh don't use mine um the

392
00:20:37,840 --> 00:20:44,200
main one to point out here that I really

393
00:20:41,000 --> 00:20:47,799
like is serve public normally that

394
00:20:44,200 --> 00:20:50,480
defaults to true what that does is it

395
00:20:47,799 --> 00:20:53,720
will uh when you request the open API

396
00:20:50,480 --> 00:20:55,280
schema you it is you see every

397
00:20:53,720 --> 00:20:59,080
possible

398
00:20:55,280 --> 00:21:01,200
um method every possible path every

399
00:20:59,080 --> 00:21:05,320
possible

400
00:21:01,200 --> 00:21:07,200
um uh serializer information that that

401
00:21:05,320 --> 00:21:11,000
would come out of your website when you

402
00:21:07,200 --> 00:21:14,880
set that to false the view the user gets

403
00:21:11,000 --> 00:21:16,720
of your open API schema is what they can

404
00:21:14,880 --> 00:21:19,360
do on the

405
00:21:16,720 --> 00:21:21,679
website which means you if you're

406
00:21:19,360 --> 00:21:23,799
providing a Reon schema to

407
00:21:21,679 --> 00:21:26,240
unauthenticated users they don't get

408
00:21:23,799 --> 00:21:28,960
confused as to why they might be able to

409
00:21:26,240 --> 00:21:30,960
post or delete website and they don't

410
00:21:28,960 --> 00:21:32,360
get confused when they then get told no

411
00:21:30,960 --> 00:21:35,159
you're not

412
00:21:32,360 --> 00:21:37,360
allowed okay we also need to plug in a

413
00:21:35,159 --> 00:21:40,320
couple of things in our uh this is my

414
00:21:37,360 --> 00:21:43,200
main uh root paths file so we've include

415
00:21:40,320 --> 00:21:47,679
the mixers URLs and we just include we

416
00:21:43,200 --> 00:21:51,240
use the spectacular API view um and then

417
00:21:47,679 --> 00:21:54,320
we uh use if you're using the Dango rest

418
00:21:51,240 --> 00:21:58,080
drf spectacular sidecar package you get

419
00:21:54,320 --> 00:22:00,279
a Swagger API for free um you include

420
00:21:58,080 --> 00:22:03,080
that and you point it to the URL name

421
00:22:00,279 --> 00:22:04,880
that we declared for the other uh open

422
00:22:03,080 --> 00:22:09,360
API

423
00:22:04,880 --> 00:22:12,799
URL uh and that allows us to generate a

424
00:22:09,360 --> 00:22:16,880
nice content and because that is a demo

425
00:22:12,799 --> 00:22:19,880
this is a demo um it gives you this nice

426
00:22:16,880 --> 00:22:20,720
uh spec that you can go in and try these

427
00:22:19,880 --> 00:22:25,240
things

428
00:22:20,720 --> 00:22:27,640
out so there's lots more uh information

429
00:22:25,240 --> 00:22:30,600
this has really just been a very basic

430
00:22:27,640 --> 00:22:33,000
introduction to how to use uh Jango rest

431
00:22:30,600 --> 00:22:36,600
framework Dr spectacular those are the

432
00:22:33,000 --> 00:22:39,360
bits that I stumbled most on um thank

433
00:22:36,600 --> 00:22:39,360
you very much for your

434
00:22:43,880 --> 00:22:51,480
time thank you very much Paul about um

435
00:22:48,440 --> 00:22:53,799
but uh that's just that's why we have

436
00:22:51,480 --> 00:22:56,640
those two particular views uh if you

437
00:22:53,799 --> 00:22:59,880
don't want to provide that particular

438
00:22:56,640 --> 00:23:03,159
output you only use the first open API

439
00:22:59,880 --> 00:23:05,919
schema and that's all you need to

440
00:23:03,159 --> 00:23:09,520
present cool we have time for one more

441
00:23:05,919 --> 00:23:09,520
question up the back

442
00:23:11,880 --> 00:23:17,080
there hi thanks for the talk let's say

443
00:23:14,840 --> 00:23:20,159
you join a hypothetical company and they

444
00:23:17,080 --> 00:23:23,320
give you ajango app and the view.py is

445
00:23:20,159 --> 00:23:25,480
6,500 lines long what would you do to

446
00:23:23,320 --> 00:23:29,600
dry it

447
00:23:25,480 --> 00:23:34,799
up I that is I'm totally sympathetic to

448
00:23:29,600 --> 00:23:37,559
that particular situation um so that's

449
00:23:34,799 --> 00:23:39,640
where I what I really like and the

450
00:23:37,559 --> 00:23:45,440
reason I approached this from the point

451
00:23:39,640 --> 00:23:48,960
of view of um taking my existing website

452
00:23:45,440 --> 00:23:53,360
and adding an API to it is it's really

453
00:23:48,960 --> 00:23:57,360
easy to just bolt on that uh mix view

454
00:23:53,360 --> 00:24:03,640
set use the router and get a simple

455
00:23:57,360 --> 00:24:06,200
output um and you can supply that as uh

456
00:24:03,640 --> 00:24:09,520
say SL API

457
00:24:06,200 --> 00:24:12,480
slv2 and now you can do ab comparison

458
00:24:09,520 --> 00:24:16,159
between uh version one and version two

459
00:24:12,480 --> 00:24:20,039
of your API to see if the queries match

460
00:24:16,159 --> 00:24:24,279
and the responses match um and I would

461
00:24:20,039 --> 00:24:29,919
just chisel away gradually adding mixes

462
00:24:24,279 --> 00:24:34,279
sorry adding um models adding view sets

463
00:24:29,919 --> 00:24:36,000
one by one um so don't try to do a whole

464
00:24:34,279 --> 00:24:39,840
don't try to replace the whole thing in

465
00:24:36,000 --> 00:24:42,679
one go just um add little bits at a time

466
00:24:39,840 --> 00:24:45,120
and the fact that uh for example with

467
00:24:42,679 --> 00:24:48,960
the track list

468
00:24:45,120 --> 00:24:52,720
um the that I can add that as a single

469
00:24:48,960 --> 00:24:57,320
field that gets expressed as a a list

470
00:24:52,720 --> 00:25:00,760
within the Json output there uh means I

471
00:24:57,320 --> 00:25:05,200
don't actually have to try to replace

472
00:25:00,760 --> 00:25:09,559
every single output in that

473
00:25:05,200 --> 00:25:12,039
um uh that big set of URLs maybe I just

474
00:25:09,559 --> 00:25:15,960
need one piece of data that contains all

475
00:25:12,039 --> 00:25:18,679
of the information that a person like or

476
00:25:15,960 --> 00:25:20,159
a a script like the UI would want to

477
00:25:18,679 --> 00:25:24,720
know about that

478
00:25:20,159 --> 00:25:27,440
mix so see yeah again uh I like the the

479
00:25:24,720 --> 00:25:29,840
approach of try to do as little as

480
00:25:27,440 --> 00:25:32,679
possible in that sort of situation see

481
00:25:29,840 --> 00:25:36,399
how uh see how

482
00:25:32,679 --> 00:25:38,120
few um view sets you can use to Pro

483
00:25:36,399 --> 00:25:40,559
provide the information that your

484
00:25:38,120 --> 00:25:40,559
customers

485
00:25:40,679 --> 00:25:48,819
want thank you very much

486
00:25:43,400 --> 00:25:48,819
[Applause]