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![www.erlang-solutions.com Why would we need a REST interconnection library? Create a user with this info: [...] 200: Success, user created Our App Server Backend](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-8-2048.jpg)
![www.erlang-solutions.com Why would we need a REST interconnection library? Update some info for this user: [...] 200: Success, returns user updated Our App Server Backend](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-9-2048.jpg)
![www.erlang-solutions.com Delete this user: [...] 200: Success, user deleted Why would we need a REST interconnection library? Our App Server Backend](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-10-2048.jpg)
![www.erlang-solutions.com User Repository User findAll() → [User] findByID(id) → User create(User) update(User) delete(User)](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-26-2048.jpg)
![www.erlang-solutions.com Elemental CRUD operations* Repository Entity findAll() → [Entity] findByID(id) → Entity create(Entity) update(Entity) delete(Entity)](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-27-2048.jpg)
![www.erlang-solutions.com Post Repository Post findAll() → [Post] findByID(id) → Post create(Post) update(Post) delete(Post) Customization findPostsFromUser(User) → [Post]](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-28-2048.jpg)
![www.erlang-solutions.com name Our Repository needs a name to work Repository Entity findAll() → [Entity] findByID(id) → Entity create(Entity) update(Entity) delete(Entity) GET /:name/ GET /:name/:id POST /:name PUT /:name/:id DELETE /:name/:id](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-31-2048.jpg)
![www.erlang-solutions.com User Repository findAll() → [User] findByID(id) → User create(User) update(User) delete(Entity) GET /users/ GET /users/:id POST /users PUT /users/:id DELETE /users/:id This name represents the group of entities that the repository works with "users" User](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-32-2048.jpg)
![www.erlang-solutions.com ● Result e. g. [User] e. g. NSError](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-46-2048.jpg)
![www.erlang-solutions.com ● Future - Let's create a function that returns a Future: This Future is going to work with a Result<[User], NSError>](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-51-2048.jpg)
![www.erlang-solutions.com - Let's use that Future: let result: (Result<[User], NSError>) Type inference let users: [User] let error: NSError](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-52-2048.jpg)
![www.erlang-solutions.com OK, let's talk about parsing... User[String: AnyObject] a.k.a. "Dictionary" conversion](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-75-2048.jpg)
![www.erlang-solutions.com To the server OK, let's talk about parsing... User[String: AnyObject] create() update() Dictionary Representable](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-76-2048.jpg)
![www.erlang-solutions.com OK, let's talk about parsing... User[String: AnyObject] read() From the server Dictionary Initializable](https://image.slidesharecdn.com/warilis-160609134510/75/Writing-a-REST-Interconnection-Library-in-Swift-77-2048.jpg)
Uploaded byPablo Villar
Writing a REST Interconnection Library in Swift
The document summarizes Pablo Luciano Villar's presentation on writing a REST interconnection library in Swift. The presentation covered the motivation for such a library, proposed an architectural concept using repositories and backends to abstract network calls, and provided an implementation example in Swift using protocols, generics, enums, and other features. Key aspects included defining a common API for CRUD operations across different entities, handling asynchronous network requests with Futures, and enhancing error handling and data parsing. The full implementation is available as an open source library called Jayme.
Writing a REST Interconnection Library in Swift
- 1. www.erlang-solutions.com SWIFTBA MEETUP JUNE 8th, 2016 @Inaka's Offices
- 2. www.erlang-solutions.com HELLO! Pablo Luciano Villar pablo@inakanetworks.com @pablolvillar www.erlang-solutions.comwww.inaka.net _iOS dev since 2011 _swifter since 2015
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- 5. www.erlang-solutions.com ROADMAP 1. Motivation 2. Architecturalconcept 3. Implementation
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- 7. www.erlang-solutions.com Why would weneed a REST interconnection library? Our App Server Backend Give me a list with all the users 200: Success, returns JSON array with users
- 8. www.erlang-solutions.com Why would weneed a REST interconnection library? Create a user with this info: [...] 200: Success, user created Our App Server Backend
- 9. www.erlang-solutions.com Why would weneed a REST interconnection library? Update some info for this user: [...] 200: Success, returns user updated Our App Server Backend
- 10. www.erlang-solutions.com Delete this user:[...] 200: Success, user deleted Why would we need a REST interconnection library? Our App Server Backend
- 11. www.erlang-solutions.com Why would weneed a REST interconnection library? C/R/U/D Response Our App Server Backend
- 12. www.erlang-solutions.com ● NSURLSession ● Alamofire/ AFNetworking ● Other libraries How we usually write networking code:
- 13. www.erlang-solutions.com NSURLSession example: "Giveme a list with all the users" GET /users How we usually write networking code:
- 14. www.erlang-solutions.com Now, where shouldthat networking code go…?
- 15. www.erlang-solutions.com Premises: ● Find agood place to put our networking code. ● Define a proper way to architecture our REST layer. ● Avoid duplicated code from common CRUD operations. ● Come up with a concise API that we can use across all of our projects.
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- 17. www.erlang-solutions.com GOAL: Provide a neatAPI that our ViewControllers can interact with without having to worry about networking implementation details.
- 18. www.erlang-solutions.com Let's find outcommon paths... "Give me a list with all the users" GET /users "Give me the details for this user" GET /users/:id "Create a user with this data" POST /users "Update this user with this data" PUT /users/:id "Delete this user" DELETE /users/:id
- 19. www.erlang-solutions.com Let's find outcommon paths... "Give me a list with all the users" GET /users "Give me the details for this user" GET /users/:id "Create a user with this data" POST /users "Update this user with this data" PUT /users/:id "Delete this user" DELETE /users/:id
- 20. www.erlang-solutions.com Let's find outcommon paths... "Give me a list with all the posts" GET /posts "Give me the details for this post" GET /posts/:id "Create a post with this data" POST /posts "Update this post with this data" PUT /posts/:id "Delete this post" DELETE /posts/:id
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- 22. www.erlang-solutions.com "Give me alist with all the entities" GET /:name "Give me the details for this entity" GET /:name/:id "Create an entity with this data" POST /:name "Update this entity with this data" PUT /:name/:id "Delete this entity" DELETE /:name/:id Let's introduce the entity concept...
- 23. www.erlang-solutions.com "Give me alist with all the entities" GET /:name "Give me the details for this entity" GET /:name/:id "Create an entity with this data" POST /:name "Update this entity with this data" PUT /:name/:id "Delete this entity" DELETE /:name/:id Notice that any entity needs an id to work
- 24. www.erlang-solutions.com User Post Comment idCreate? Read? Update? Delete? Entity
- 25. www.erlang-solutions.com REPOSITORY! Actually, we needa different place from which we can perform CRUD operations to our entity… Entity Create Read Update Delete And that place is called…
- 26. www.erlang-solutions.com User Repository User findAll() → [User] findByID(id)→ User create(User) update(User) delete(User)
- 27. www.erlang-solutions.com Elemental CRUD operations* Repository Entity findAll()→ [Entity] findByID(id) → Entity create(Entity) update(Entity) delete(Entity)
- 28. www.erlang-solutions.com Post Repository Post findAll() → [Post] findByID(id)→ Post create(Post) update(Post) delete(Post) Customization findPostsFromUser(User) → [Post]
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- 30. www.erlang-solutions.com This one hasthe issue that every repository you create will come with all these basic CRUD methods by default, even if any particular repository doesn't need all of them. That breaks the YAGNI principle. But still, it's a very convenient approach for us. * There are many ways to approach the Repository pattern.
- 31. www.erlang-solutions.com name Our Repository needsa name to work Repository Entity findAll() → [Entity] findByID(id) → Entity create(Entity) update(Entity) delete(Entity) GET /:name/ GET /:name/:id POST /:name PUT /:name/:id DELETE /:name/:id
- 32. www.erlang-solutions.com User Repository findAll() → [User] findByID(id)→ User create(User) update(User) delete(Entity) GET /users/ GET /users/:id POST /users PUT /users/:id DELETE /users/:id This name represents the group of entities that the repository works with "users" User
- 33. www.erlang-solutions.com Last, but notleast… We still need to define a place where our networking code will fall into. Let's introduce the concept of… BACKEND
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- 41. www.erlang-solutions.com Let's translate all thesediagrams into code. Not just any code, but… Swiftcode!
- 42. www.erlang-solutions.com Where to start…? OK,let's do Repository
- 43. www.erlang-solutions.com ✔ Protocol composition ✔Generics - Prefer composition over inheritance whenever possible. - This way, you end up having a more flexible and extendable architecture. - By using generics, you lead your models to become more adaptive and customizable. - The final user is going to be happier.
- 44. www.erlang-solutions.com Before proceeding, let'sintroduce two new friends you should become familiar with... ● Result ● Future
- 45. www.erlang-solutions.com ● Result - It'san enum that we're going to use to represent a result. - It can be either: - Success (and hold a relevant result value) - Failure (and hold a relevant error)
- 46. www.erlang-solutions.com ● Result e. g.[User] e. g. NSError
- 47. www.erlang-solutions.com ● Future - Youshould definitely check out this talk: - https://realm.io/news/swift-summit-javier-soto-futures/ - Anyway, roughly speaking, a Future is a struct that we're going to use to represent the computation of an asynchronous task.
- 48. www.erlang-solutions.com - Here youcan see why it's convenient to use Futures:
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- 50. www.erlang-solutions.com .map and .andThenare 2 special functions in Futures that allow us to chain asynchronous operations very nicely.
- 51. www.erlang-solutions.com ● Future - Let'screate a function that returns a Future: This Future is going to work with a Result<[User], NSError>
- 52. www.erlang-solutions.com - Let's usethat Future: let result: (Result<[User], NSError>) Type inference let users: [User] let error: NSError
- 53. www.erlang-solutions.com ✔ Static typing/ Type inference ✔ Enums with associated values - Compiler enforces you to use the types you're expected to use. - Write less, know more. - We're getting all the juice from Swift enums by using them with associated values. - This allows us to define powerful structures to represent discrete values containing relevant information in a proper way.
- 54. www.erlang-solutions.com Now, let's addelemental CRUD functionality to our Repository...
- 55. www.erlang-solutions.com We can adddefault implementations for those in a protocol extension:
- 56. www.erlang-solutions.com Let's analyze howwe would implement one of those…
- 57. www.erlang-solutions.com Let's add aBackend at the Repository level...
- 58. www.erlang-solutions.com Let's define aBackend: Associated type: String Means that any case will have a .rawValue of type String. "GET" "POST" "PUT" "DELETE" come by default
- 59. www.erlang-solutions.com Let's (finally) adda Backend at the Repository level...
- 60. www.erlang-solutions.com let future: Future<NSData?, NSError> Typeinference ≠Parsing
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- 63. www.erlang-solutions.com Now, let's definea concrete Backend that we can actually use...
- 64. www.erlang-solutions.com Now, let's definea concrete Backend that we can actually use...
- 65. www.erlang-solutions.com URL checking We're goingto improve this. Later. Promise. Server linking Dependency
- 66. www.erlang-solutions.com We need variablesto hold these. Also, it would be cool to be able to inject them.
- 67. www.erlang-solutions.com Let's go backa bit to our NSURLSessionBackend definition... We need to hold state, so we need a class.
- 68. www.erlang-solutions.com Let's define ourconfiguration object
- 69. www.erlang-solutions.com We can useconstructor injection in our NSURLSessionBackend... With default values Remember: Using dependency injection helps unit-testing.
- 70. www.erlang-solutions.com ✔ Dependency Injection ✔Enums with raw values - Initializers with default values in their parameters encourage constructor injection. - Once again, Swift eases unit-testing. - Enums can be associated to a type so that their cases hold a .rawValue of that type. - You can define their raw values by your own, or let the compiler do its magic and use the defaults.
- 71. www.erlang-solutions.com Now the questionis, why the hell are we still using NSError??
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- 73. www.erlang-solutions.com Let's enhance ourerror handling... All of these do not appear as errors in the networking process... We usually get a success response with a status code that WE should interpret as an error, depending on the code (e.g. a 500).
- 74. www.erlang-solutions.com Now, let's talkabout parsing... Do I have time to talk about this? YES / NO
- 75. www.erlang-solutions.com OK, let's talkabout parsing... User[String: AnyObject] a.k.a. "Dictionary" conversion
- 76. www.erlang-solutions.com To the server OK, let'stalk about parsing... User[String: AnyObject] create() update() Dictionary Representable
- 77. www.erlang-solutions.com OK, let's talkabout parsing... User[String: AnyObject] read() From the server Dictionary Initializable
- 78. www.erlang-solutions.com From dictionary /To dictionary In case there's a parsing error (e.g. a missing field). Remember: You should NEVER initialize an invalid object.
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- 81. www.erlang-solutions.com ✔ ErrorType ✔ Throws -Error handling has been enhanced in Swift. - Now you can define your own errors, which combined with the power of enums and pattern matching allow you to work in a cleaner way. - Throwable initializers encourage better exceptions handling mechanisms, such as try/catch. - As we saw, you can make your initializers throw any discrete ErrorType that you define.
- 82. www.erlang-solutions.com https://github.com/inaka/JaymeMeet Jayme ✓ OpenSource ✓ Issues are welcome ✓ So are Pull Requests Jayme is basically what we just built, with some other enhancements that I haven't talked about because of time, for example: ● Pagination support (PagedRepository) ● More generalization (Backend is more abstract)
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