Building a Swift Web API and Application Together

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Building a Swift Web API and Application Together Kyle Fuller

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Agenda —API Design —Building API in Swift —Deploying API in Swift in production

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API Design

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What makes a good API?

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What makes a good API? —Decoupled from implementation details —Able to evolve without breaking existing clients

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Example: Pagination

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GET /posts

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GET /posts{?page}

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GET /posts?page=2

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! How can we solve?

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GET /posts{?before}

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GET /posts?before=44

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How do we introduce changes to our API?

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Versioning APIs

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/v1/posts{?page} /v2/posts{?before}

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/posts{?page} /posts{?before}

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API is coupled to implementation details

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API is coupled to implementation details

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What happens when you version an API?

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What happens when you version an API?

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How can we design the API without exposing implementation details?

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REST Representational State Transfer

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Anticipating change is one of the central themes of REST

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Evolvability

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Tight Coupling

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"You can’t have evolvability if clients have their controls baked into their design at deployment"

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"Controls have to be learned on the ﬂy. That’s what hypermedia enables"

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Hypermedia

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Web Linking RFC 5988

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GET /posts Link: ; rel="next", ; rel="last"

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GET /posts?before=120 Link: ; rel="prev", ; rel="first"

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WebLinking.swift https://github.com/kylef/WebLinking.swift

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WebLinking: Checking for next link if let link = response.findLink(relation: "next") { print("We have a next link with the URI: \(link.uri).") }

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WebLinking: Introspecting Available Links for link in response.links { print("Relation: \(link.relationType)") print("URI: \(link.uri)") }

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application/hal+json

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Blog Post { "title": "My First Blog Post", "body": "Lorem Ipsum" }

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Blog Post (Next Link) { "title": "My First Blog Post", "body": "Lorem Ipsum", "_links": [ { "href": "/posts/2", "relation": "next" } ] }

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Blog Post (Self) { "title": "My First Blog Post", "body": "Lorem Ipsum", "_links": [ { "href": "/posts/1", "relation": "self" }, { "href": "/posts/2", "relation": "next" } ] }

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Blog Post (Comments) { "title": "My First Blog Post", "body": "Lorem Ipsum", "_links": [ { "href": "/posts/1", "relation": "self" }, { "href": "/posts/2", "relation": "next" }, { "href": "/posts/1/comments", "relation": "comments" }, ] }

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Blog Post (Embedded Comments) { "_embed": { "comments": [ { "author": "Kyle", "body": "That's a really interesting post!" "_links": [ { "href": "/posts/1/comments/1", "relation": "self" } ] } ] } }

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application/ vnd.siren+json

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Delete Post { "properties": { "title": "My First Blog Post", "body": "Lorem Ipsum", }, "actions": [ { "name": "delete", "method": "DELETE", "href": "/posts/1" } ] }

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Delete Post { "properties": { "title": "My First Blog Post", "body": "Lorem Ipsum", }, "actions": [ { "name": "delete", "method": "DELETE", "href": "/posts/1" } ] }

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Create Comment { "properties": { "title": "My First Blog Post", "body": "Lorem Ipsum", }, "actions": [ { "name": "comment", "method": "POST", "href": "/posts/1/comments", "fields": [ { "name": "author", "type": "string" }, { "name": "message", "type": "string" } ] } ] }

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Create Comment (Logged in) { "properties": { "title": "My First Blog Post", "body": "Lorem Ipsum", }, "actions": [ { "name": "comment", "method": "POST", "href": "/posts/1/comments", "fields": [ { "name": "message", "type": "string" } ] } ] }

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Hypermedia —Remove implementation details from interface —Keep business logic on back-end, not front-end

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Building an API in Swift

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Web Frameworks

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Web Frameworks —Frank —IBM Kitura —Vapor

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Frank vs Kitura vs Vapor

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Frank get("users", *) { (request, username: String) in return "Hello \(username)" }

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Server APIs Working Group

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Server APIs Working Group

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Useful Tools —Templating Languages —Stencil —Data Persistence —Redis (Redbird) —PostgreSQL

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Testing

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XCTest class PersonTests: XCTestCase { let person = Person(name: "Kyle") func testPersonName() { XCTAssertEqual(person.name, "Kyle") } func testPersonDescription() { XCTAssertEqual(person.description, "Kyle") } }

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extension PersonTests: XCTestCaseProvider { var allTests : [(String, () throws -> Void)] { return [ ("testPersonName", testPersonName), ("testPersonDescription", testPersonDescription), ] } } XCTMain([ PersonTests(), ])

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Dredd https://github.com/apiaryio/dredd

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API Blueprint # GET /hello + Response 200 (application/json) { "name": "Kyle" }

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Dredd Testing $ dredd \ apidescription.apib \ https://localhost:8080 ✔ GET /hello ✔ API Matches API Description

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Deployment

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https://github.com/kylef/heroku-buildpack-swift

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$ cat Package.swift import PackageDescription let package = Package( name: "Hello", dependencies: [ .Package(url: "https://github.com/nestproject/Frank.git", majorVersion: 0, minor: 3), ] )

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$ cat Sources/main.swift import Frank get { _ in return "Hello World" } get(*) { (_, username: String) in return "Hello \(username)" }

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$ cat Sources/main.swift import Frank get { _ in return "Hello World" } get(*) { (_, username: String) in return "Hello \(username)" }

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$ cat .swift-version 3.0.2

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$ cat .swift-version 3.0.2

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$ swift build $ .build/debug/Hello [INFO] Listening at http://0.0.0.0:8000 (48827) [INFO] Booting worker process with pid: 48828

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$ cat Procfile web: Hello

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$ heroku create --buildpack https://github.com/kylef/heroku-buildpack-swift.git $ git push heroku master remote: -----> Swift app detected remote: -----> Installing 3.0.2 remote: -----> Installing clang-3.7.0 remote: -----> Building Package remote: -----> Copying binaries to 'bin'

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Manual Deployment

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Monitoring

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Logging

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print("ERROR: Connection to database failed \(error)")

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Papertrail

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Conclusion —API Design —Swift Web Services —Tools & Frameworks —Testing —Deployment —Monitoring

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Conclusion —API Design —Swift Web Services —Tools & Frameworks —Testing —Deployment —Monitoring

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kylefuller https://fuller.li/talks