Embracing Change - MBLTDev 2015

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EMBRACING CHANGE KYLE FULLER

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POLLS

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HOW DOES IT WORK?

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GET /questions

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DELETE /questions/{id}

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GET /questions/{id}

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POST /questions/{id}/choices/{choice_id}

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POST /questions

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APPLICATION WAS BUILT FROM AN OUT-OF-BAND SPECIFICATION

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TIGHT COUPLING

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WE WANT TO CHANGE SOMETHING.

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YOUR BOSS FINDS YOU LATE ON A FRIDAY AFTERNOON

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I'D LIKE TO...

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> Add validation to create question with a minimum of 2 choices

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> Add a minimum or maximum length to questions

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> Change delete so only admins can delete questions

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> Change delete so you can only delete your own questions

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> Change delete so you can't delete the initial questions

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> Change vote so you can only vote once per question

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> Change vote so any new votes override old votes on the same question

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> Add a new report question feature

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THIS WILL TAKE SOME TIME...

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BUSINESS LOGIC

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I HAVE TO REWRITE X

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"ANTICIPATING CHANGE IS ONE OF THE CENTRAL THEMES OF REST"

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REPRESENTATIONAL STATE TRANSFER

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OUR API https://polls.apiblueprint.org/

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OUR API > Questions (affordance)

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QUESTIONS > questions > create (affordance)

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QUESTION > question > choices > delete (affordance) > report (affordance)

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CHOICE > choice > votes (count) > vote (affordance)

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SEMANTICS NOT IMPLEMENTATION DETAILS

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$ curl https://polls.apiblueprint.org/ {"questions_url": "/questions", "url": "/"}

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HAL application/hal+json

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HAL $ curl https://polls.apiblueprint.org/ -H 'Accept: application/hal+json' { "_links": { "questions": { "href": "/questions" }, "self": { "href": "/" } } }

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HAL $ curl https://polls.apiblueprint.org/questions/1 -H 'Accept: application/hal+json' { "question": "Favourite programming language?", "_links": {"self": {"href": "/questions/1"}}, "_embed": { "choices": [ { "_links": {"self": {"href": "/questions/1/choices/1"}}, "choice": "Swift", "votes": 483 } ] } }

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$ curl https://polls.apiblueprint.org/questions -H 'Accept: application/hal+json' { "_links": { "first": {"href": "/questions"}, "self": {"href": "/questions"}, "next": {"href": "/questions?page=2"} "last": {"href": "/questions?page=2"}, }, }

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SIREN application/siren+json

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SIREN { "actions": [ { "name": "vote", "href": "/questions/1/choices/3", "method": "POST" } ] }

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SIREN { "actions": [ { "name": "create", "method": "POST", "type": "application/json", "href": "/questions", "fields": [ { "name": "question", "type": "text", "title": "Question" }, { "name": "choices", "type": "array[text]", "title": "Choices" } ] } ] }

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HYPERDRIVE

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API BLUEPRINT + HYPERDRIVE

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API BLUEPRINT ## Questions Collection [/questions] ### Create a new question [POST] + Relation: create + Request (application/json) + Attributes + question (string, required) + choices (array[string], required) + Response 201 (application/json) + Attributes (Question)

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HYPERDRIVE hyperdrive.enter("https://polls.apiblueprint.org/") { result }

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REPRESENTOR

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DEMO

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hyperdrive.enter("http://localhost:8000/") // follow the 'questions' transition .flatMap { hyperdrive.request($0.transitions["questions"]) } // Follow the 'create' transition .flatMap { hyperdrive.request($0.transitions["create"], attributes: [ "question": "types of egg", "choices": ["hard boiled eggs", "soft boiled eggs"] ]) } // Select the first choice .map { $0.representors["choices"]!.first! } // Follow the 'vote' transition .flatMap { hyperdrive.request($0.transitions["vote"]) }

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DEMO

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/// Returns whether the user may create a question var canCreateQuestion: Bool { return representor.transitions["create"] != nil }

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/// Returns whether the user may delete the question at the given index func canDeleteQuestion(index: Int) -> Bool { let transition = questions?[index].transitions["delete"] return transition != nil }

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import JSONSchema let schema = Schema([ "type": "object", "properties": [ "question": ["type": "string"], "choices": ["type": "array", "minItems": 2], ], ]) schema.validate([ "question": "Favourite Conference?", "choices": [ "MBLTDev 2015" ] ])

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> the-hypermedia-project / Hyperdrive > kylef / Starship, RxHyperdrive, JSONSchema.swift > apiaryio / polls-app, polls-api

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> kylefuller > kyle @ fuller.li > fuller.li / slides