neothxt/snowdrop

Meet **Snowdrop** - type-safe, easy to use framework powered by Swift Macros created to let you build and maintain complex network requests with ease.

Installation

Snowdrop is available via SPM. It works with iOS Deployment Target 14.0 or later and macOS Deployment Target 11 or later.

Key Functionalities

Type-safe service creation with @Service macro
Support for various request method types such as

- @GET - @POST - @PUT - @DELETE - @PATCH - @CONNECT - @HEAD - @OPTIONS - @QUERY - @TRACE

SSL/Certificate pinning
Interceptors
Mockable

Basic Usage

Service Declaration

Creating network services with Snowdrop is really easy. Just declare a protocol along with its functions.

@Service
protocol MyEndpoint {

    @GET(url: "/posts")
    @Headers(["X-DeviceID": "testSim001"])
    func getAllPosts() async throws -> [Post]
}

If your request includes some dynamic values, such as id, you can add it to your path wrapping it with {}. Snowdrop will automatically bind your function declaration's arguments with those you include in request's path.

@GET(url: "/posts/{id}")
func getPost(id: Int) async throws -> Post

Request Execution

Upon expanding macros, Snowdrop creates a class MyEndpointService which implements MyEndpoint protocol and generates all the functions you declared.

class MyEndpointService: MyEndpoint {
    func getAllPosts() async throws -> [Post] {
        // auto-generated body
    }
    
    func getPost(id: Int) async throws -> Post {
        // auto-generated body
    }
}

Please note that if your service protocol already have "Service" keyword like MyEndpointService, macro will then generate the class named MyEndpointServiceImpl instead.

To send requests, just initialize MyEndpointService instance and call function corresponding to the request you want to execute.

let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!)
let post = try await service.getPost(id: 7)

Advanced Usage

### Default JSON Decoder

If you need to change default json decoder, you can set your own decoder when creating an instance of your service.

```Swift
let decoder = CustomJSONDecoder()
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!, decoder: decoder)
```

#### SSL/Certificate Pinning

Snowdrop offers SSL/Certificate pinning functionality when executing network requests. You can turn it on/off when creating an instance of your service. You can also determine urls that should be excluded from pinning.

```Swift
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!, pinningMode: .ssl, urlsExcludedFromPinning: ["https://my-endpoint.com/about"])
```

### Body Argument

If you want to put some encodable object as a body of your request, you can either put it in your declaration as "body" argument or - if you want to use another name - use `@Body` macro like:

```Swift
@POST(url: "/posts")
@Body("model")
func addPost(model: Post) async throws -> Data
```

### File Upload using form-data

If you want to declare service's function that sends some file to the server as `multipart/form-data`, use `@FileUpload` macro. It'll automatically add `Content-Type: multipart/form-data` to the request's headers and extend the list of your function's arguments with `_payloadDescription: PayloadDescription` which you should then use to provide information such as `name`, `fileName` and `mimeType`.
For mime types such as jpeg, png, gif, tiff, pdf, vnd, plain, octetStream, you don't have to provide `PayloadDescription`. Snowdrop can automatically recognize them and create `PayloadDescription` for you.

```Swift
@Service
protocol MyEndpoint {

    @FileUpload
    @Body("image")
    @POST(url: "/uploadAvatar/")
    func uploadImage(_ image: UIImage) async throws -> Data
}

let payload = PayloadDescription(name: "avatar", fileName: "filename.jpeg", mimeType: "image/jpeg")
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!)
_ = try await service.uploadImage(someImage, _payloadDescription: payload)
```

### Query Parameters

With Snowdrop, you can pass your query params in two ways.

First one is to use `@QueryParams` macro. To inform which arguments of your func are supposed to be query params, put them in array like this:

```Swift
@Service
protocol MyEndpoint {
    @GET(url: "/posts/{id}")
    @QueryParams(["author"])
    func getPost(id: Int, author: String) async throws -> Post
}

let authorName = "John Smith"
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!)
let post = try await service.getPost(id: 7, author: authorName)
```

Alternatively, upon expanding macros, Snowdrop adds argument `_queryItems: [QueryItem]` to every service's function. Use it like this:

```Swift
@Service
protocol MyEndpoint {
    @GET(url: "/posts/{id}")
    func getPost(id: Int) async throws -> Post
}

let authorName = "John Smith"
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!)
let post = try await service.getPost(id: 7, _queryItems: [.init(key: "author", value: authorName)])
```

### Arguments' Default Values

Snowdrop allows you to define custom values for your arguments. Let's say your path includes `{id}` argument. As you already know by now, Snowdrop automatically associates it with `id` argument of your `func` declaration. If you want it to have default value equal "3", do it like: `{id=3}`. Be careful though as Snowdrop won't check if your default value's type conforms to the declaration.  
When inserting `String` default values such as {name="Some name"}, it is strongly recommended to use `Raw String` like `@GET(url: #"/authors/{name="John Smith"}"#)`.

### Interceptors

Each service provides two methods to add interception blocks - `addBeforeSendingBlock` and `addOnResponseBlock`. Both accept arguments such as `path` of type `String` and `block` which is closure.

To add `addBeforeSendingBlock` or `addOnResponseBlock` for a requests matching certain path, use regular expressions like:

```Swift
service.addBeforeSendingBlock(for: "my/path/[0-9]{1,}/content") { urlRequest in
    // some operations
    return urlRequest
}
```

To add `addBeforeSendingBlock` or `addOnResponseBlock` for ALL requests, do it like:

```Swift
service.addOnResponseBlock { data, httpUrlResponse in
    // some operations
    return data
}
```

**Note that if you add interception block for a certain request path, general interceptors will be ignored.**

### Mockable

If you'd like to create mockable version of your service, Snowdrop got you covered. Just add `@Mockable` macro to your service declaration like

```Swift
@Service
@Mockable
protocol Endpoint {
    @Get("/path")
    func getPosts() async throws -> [Posts]
}
```

Snowdrop will automatically create a `EndpointServiceMock` class with all the properties `Service` should have and additional properties such as `getPostsResult` to which you can assign value that should be returned.

#### Sample usage:

```Swift
func testEmptyArrayResult() async throws {
    let mock = EndpointServiceMock(baseUrl: URL(string: "https://some.url")!
    mock.getPostsResult = .success([])

    let result = try await mock.getPosts()
    XCTAssertTrue(result.isEmpty)
}
```

**Note that mocked methods will directly return stubbed result without accessing Snowdrop.Core so your beforeSend and onResponse blocks won't be called.**

### JSON Injection

If you'd like to test your service against mocked JSONs, you can easily do it. Just make sure you got your JSON mock somewhere in your project files, then instantiate your service and determine for which request your mock should be injected like in the example below.

```Swift
func testJSONMockInjectsion() async throws {
    let service = MyEndpointService(baseUrl: someBaseURL)
    service.testJSONDictionary = ["users/123/info": "MyJSONMock"]
    
    let result = try await service.getUserInfo(id: 123)
    XCTAssertTrue(result.firstName, "JSON")
    XCTAssertTrue(result.lastName, "Bourne")
}
```

### Verbose

If you'd like to get see logs from Snowdrop, use `verbose` flag when creating new instance of your service.

```Swift
let service = MyEndpointService(baseUrl: URL(string: "https://my-endpoint.com")!, verbose: true)
```

Acknowledgements

Retrofit was an inspiration for Snowdrop.

Package Metadata

Repository: neothxt/snowdrop

Default branch: main

README: README.md