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Embracing Change with REST Kyle Fuller

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Representational State Transfer

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What is REST?

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Roy Fielding

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“Anticipating change is one of the central themes of REST”

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"Move fast and break things" Mark Zuckerberg, Facebook

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"Each version will remain for at least 2 years from release." Facebook

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Move Fast, Break Nothing

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REST is not... 4 CRUD 4 Pretty URLs 4 JSON 4 HTTP Verbs 4 Routing

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It’s not about exposing your database

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But... we design apps this way

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Actually, We Don't

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We design implementations this way

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Todo 4 id 4 title 4 status

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Designing API by exposing implementation details

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Designing API by exposing implementation details

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We could design via states

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How do we Transfer State from Server to Client?

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We transfer Representations of State

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Hence Representational State Transfer

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How do we transfer state transitions?

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HATEOAS

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HATEOAS Hypermedia as the Engine of Application State

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Relations

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Transitions

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"HATEOAS" is a REST constraint.

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Not an option. Not an ideal. Hypermedia is a constraint.

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As in, you either do it or you aren’t doing REST.

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GET http://polls.com/

Things you can do

Make a new question

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GET http://polls.com/

Things you can do

Make a new question

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Creating a question the bad way 4 Construct a 'new question' URL 4 Submit a form given our pre-existing knowledge of how it may look 4 Visit the page (it may or may not work)

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with hypermedia 4 We’re offered to create a question 4 Fill in the form it gives you 4 Submit the form

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Exactly how you browse the web

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Clients can have the same benefits by doing this too

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Polls

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Questions 4 create 4 list

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Question 4 delete 4 choices

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Choice 4 vote

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One Does Not Simply Use JSON

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Hypermedia Formats 4 HAL (application/hal+json) 4 Siren (application/vnd.siren+json)

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Siren Link { "links": [ { "rel": ["next"], "href": "/questions?page=2" } ] }

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Siren Link { "links": [ { "rel": ["choice"], "href": "/questions/1/choices/1" } ] }

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Siren Link { "entities": [ { "links" { { "rel": ["self"], "href": "/questions/1/choices/1" } }, "rel": ["choices"], "properties": {"choice": "Swift", "votes": 22} } ] }

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Siren Link { "entities": [ { "rel": ["choices"], "properties": {"choice": "Swift", "votes": 22}, "actions": [ { "href": "/questions/1/choices/1", "name": "vote", "method": "POST" } ] } ] }

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Siren Action { "actions": { "create": { "href": "/questions", "method": "POST", "fields": [ { "name": "question" }, { "name": "choices" } ] } } }

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Siren Action { "actions": { "create": { "href": "/questions", "method": "POST", "fields": [ { "name": "question" }, { "name": "choices" } ], "type": "application/x-www-form-urlencoded" } } }

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Siren Action { "actions": { "create": { "href": "/questions", "method": "POST", "fields": [ { "name": "question" }, { "name": "choices" } ], "type": "application/json" } } }

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{ "actions": { "create": { "href": "/questions", "method": "POST", "fields": [ { "name": "question" }, { "name": "choices" } ], "type": "application/json" } } }

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Ability to change implementation details

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Ability to change implementation details 4 Change URIs of resources (/polls/{id} -> / questions/{slug})

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Ability to change implementation details 4 Change URIs of resources (/polls/{id} -> / questions/{slug}) 4 Change HTTP methods (PUT -> PATCH)

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Ability to change implementation details 4 Change URIs of resources (/polls/{id} -> / questions/{slug}) 4 Change HTTP methods (PUT -> PATCH) 4 Change the content-type

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Ability to change implementation details 4 Change URIs of resources (/polls/{id} -> / questions/{slug}) 4 Change HTTP methods (PUT -> PATCH) 4 Change the content-type 4 Change fields used in forms

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Teach Clients Semantic meaning of the Domain

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Don’t hard-code implementation details

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Demo

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Representor https://github.com/the-hypermedia-project/representor-swift

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Using a transition if let transition = representor.transitions["create"] { }

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Using a transition if let transition = representor.transitions["create"] { } else { // Gracefully handle the lack of this transition }

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Using a transition if let transition = representor.transitions["create"] { transition.attributes }

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Using a transition if let transition = representor.transitions["create"] { transition.method transition.uri transition.suggestedContentType }

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Performing a Transition request(transition, attributes:[ "question": "Favourite programming language?", "choices": [ "Swift", "Python", ] ])

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REST

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Resources 4 REST APIs must be hypertext driven 4 Representor 4 Roy Fielding on Versioning 4 Polls API 4 rivr rest 4 Solving Fizz Buzz with Hypermedia

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Kyle Fuller ! fuller.li/slides ! [email protected]