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<p align="center">Declarative, easy-to-use and safe Dependency Injection framework for Swift (iOS/macOS/Linux)</p>

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<a href="https://youtu.be/Rxhc9VJBoOI" alt="Watch the demo" target="_blank"> <img src="weaver.gif" alt="Watch the video" width="960" style="display: block; margin: 0 auto" /> </a>

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If you're looking for a step by step tutorial, check out these links.

Dependency Injection

Dependency Injection basically means "giving an object its instance variables" ¹. It seems like it's not such a big deal, but as soon as a project gets bigger, it gets tricky. Initializers become too complex, passing down dependencies through several layers becomes time consuming and just figuring out where to get a dependency from can be hard enough to give up and finally use a singleton.

However, Dependency Injection is a fundamental aspect of software architecture, and there is no good reason not to do it properly. That's where Weaver can help.

What is Weaver?

Weaver is a declarative, easy-to-use and safe Dependency Injection framework for Swift.

How does Weaver work?

                                                                         |-> validate() -> valid/invalid 
swift files -> scan() -> [Token] -> parse() -> AST -> link() -> Graph -> | 
                                                                         |-> generate() -> source code 

Weaver scans the Swift sources of the project, looking for annotations, and generates an AST (abstract syntax tree). It uses SourceKitten which is backed by Apple's SourceKit.

The AST then goes through a linking phase, which outputs a dependency graph.

Some safety checks are then performed on the dependency graph in order to ensure that the generated code won't crash at runtime. Issues are friendly reported in Xcode to make their correction easier.

Finally, Weaver generates the boilerplate code which can directly be used to make the dependency injections happen.

Installation

(1) - Weaver command

Weaver can be installed using Homebrew, CocodaPods or manually.

Binary form

Download the latest release with the prebuilt binary from release tab. Unzip the archive into the desired destination and run bin/weaver

Homebrew

$ brew install weaver

CocoaPods

Add the following to your Podfile:

pod 'WeaverDI'

This will download the Weaver binaries and dependencies in Pods/ during your next pod install execution and will allow you to invoke it via ${PODS_ROOT}/WeaverDI/weaver/bin/weaver in your Script Build Phases.

This is the best way to install a specific version of Weaver since Homebrew cannot automatically install a specific version.

Mint

To use Weaver via Mint, prefix the normal usage with mint run scribd/Weaver like so:

mint run scribd/Weaver version

To use a specific version of Weaver, add the release tag like so:

mint run scribd/Weaver@1.0.7 version

Building from source

Download the latest release source code from the release tab or clone the repository.

In the project directory, run brew update && brew bundle && make install to build and install the command line tool.

Check installation

Run the following to check if Weaver has been installed correctly.

$ weaver swift --help

Usage:

    $ weaver swift

Options:
    --project-path - Project's directory.
    --config-path - Configuration path.
    --main-output-path - Where the swift code gets generated.
    --tests-output-path - Where the test helpers gets generated.
    --input-path - Paths to input files.
    --ignored-path - Paths to ignore.
    --cache-path - Where the cache gets stored.
    --recursive-off
    --tests - Activates the test helpers' generation.
    --testable-imports - Modules to imports in the test helpers.
    --swiftlint-disable-all - Disables all swiftlint rules.

(2) - Weaver build phase

In Xcode, add the following command to a command line build phase:

weaver swift --project-path $PROJECT_DIR/$PROJECT_NAME --main-output-path output/relative/path

Important - Move this build phase above the Compile Source phase so that Weaver can generate the boilerplate code before compilation happens.

Basic Usage

For a more complete usage example, please check out the sample project.

Let's implement a simple app displaying a list of movies. It will be composed of three noticeable objects:

Let's get into the code.

AppDelegate with comment annotations:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    private let dependencies = MainDependencyContainer.appDelegateDependencyResolver()
    
    // weaver: movieManager = MovieManager <- MovieManaging
    // weaver: movieManager.scope = .container
    
    // weaver: moviesViewController = MoviesViewController <- UIViewController
    // weaver: moviesViewController.scope = .container
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow()

        let rootViewController = dependencies.moviesViewController
        window?.rootViewController = UINavigationController(rootViewController: rootViewController)
        window?.makeKeyAndVisible()
        
        return true
    }
}

AppDelegate registers two dependencies:

These dependencies are made accessible to any object built from AppDelegate because their scope is set to container:

A dependency registration automatically generates the registration code and one accessor in AppDelegateDependencyContainer, which is why the rootViewController can be built:

AppDelegate with property wrapper annotations:

Since Weaver 1.0.1, you can use property wrappers instead of annotations in comments.

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    
    // Must be declared first!
    private let dependencies = MainDependencyContainer.appDelegateDependencyResolver()

    @Weaver(.registration, type: MovieManager.self, scope: .container)
    private var movieManager: MovieManaging
	
    @Weaver(.registration, type: MoviesViewController.self, scope: .container)
    private var moviesViewController: UIViewController
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow()

        window?.rootViewController = UINavigationController(rootViewController: moviesViewController)
        window?.makeKeyAndVisible()
        
        return true
    }
}

MovieManager:

protocol MovieManaging {
    
    func getMovies(_ completion: @escaping (Result<Page<Movie>, MovieManagerError>) -> Void)
}

final class MovieManager: MovieManaging {

    func getMovies(_ completion: @escaping (Result<Page<Movie>, MovieManagerError>) -> Void) {
        // fetches movies from the server...
        completion(.success(movies))        
    }
}

MoviesViewController with comment annotations:

final class MoviesViewController: UIViewController {
    
    private let dependencies: MoviesViewControllerDependencyResolver
    
    private var movies = [Movie]()
    
    // weaver: movieManager <- MovieManaging
    
    required init(injecting dependencies: MoviesViewControllerDependencyResolver) {
        self.dependencies = dependencies
        super.init(nibName: nil, bundle: nil)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Setups the tableview... 
        
        // Fetches the movies
        dependencies.movieManager.getMovies { result in
            switch result {
            case .success(let page):
                self.movies = page.results
                self.tableView.reloadData()
                
            case .failure(let error):
                self.showError(error)
            }
        }
    }

    // ... 
}

MoviesViewController declares a dependency reference:

This annotation generates an accessor in MoviesViewControllerDependencyResolver, but no registration, which means MovieManager is not stored in MoviesViewControllerDependencyContainer, but in its parent (the container from which it was built). In this case, AppDelegateDependencyContainer.

MoviesViewController also needs to declare a specific initializer:

This initializer is used to inject the DI Container. Note that MoviesViewControllerDependencyResolver is a protocol, which means a fake version of the DI Container can be injected when testing.

MoviesViewController with property wrapper annotations:

final class MoviesViewController: UIViewController {
    
    private var movies = [Movie]()

    @Weaver(.reference)
    private var movieManager: MovieManaging
    
    required init(injecting _: MoviesViewControllerDependencyResolver) {
        super.init(nibName: nil, bundle: nil)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Setups the tableview... 
        
        // Fetches the movies
        movieManager.getMovies { result in
            switch result {
            case .success(let page):
                self.movies = page.results
                self.tableView.reloadData()
                
            case .failure(let error):
                self.showError(error)
            }
        }
    }

    // ... 
}

API

Code Annotations

Weaver allows you to declare dependencies by annotating the code with comments like // weaver: ... or property wrappers like @Weaver(...) var ...

It currently supports the following annotations:

- Registration

Example:

// weaver: dependencyName = DependencyConcreteType <- DependencyProtocol

@Weaver(.registration, type: DependencyConcreteType.self) 
var dependencyName: DependencyProtocol

or

// weaver: dependencyName = DependencyConcreteType

@Weaver(.registration) 
var dependencyName: DependencyConcreteType

- Reference

Adds an accessor for the dependency to the container's protocol.

Example:

// weaver: dependencyName <- DependencyType

@Weaver(.reference) 
var dependencyName: DependencyType

DependencyType: Either the concrete or abstract type of the dependency. This also defines the type the dependency's accessor returns.

- Parameter

Adds a parameter to the container's resolver protocol. This means that the generated container needs to take these parameter at initialisation. It also means that all the concerned dependency accessors need to take this parameter.

Example:

// weaver: parameterName <= ParameterType

@Weaver(.parameter) 
var parameterName: ParameterType

- Scope

Sets the scope of a dependency. The default scope being container. Only works for registrations or weak parameters.

The scope defines a dependency lifecycle. Four scopes are available:

Example:

// weaver: dependencyName.scope = .scopeValue

@Weaver(.registration, scope: .scopeValue)
var dependencyName: DependencyType

scopeValue: Value of the scope. It can be one of the values described above.

- Custom Builder

Overrides a dependency's default initialization code.

Works for registration annotations only.

Example:

// weaver: dependencyName.builder = DependencyType.make

@Weaver(.registration, builder: DependencyType.make) 
var dependencyName: DependencyType

DependencyType.make: Code overriding the dependency's initialization code taking DependencyTypeInputDependencyResolver as a parameter and returning DependencyType (e.g. make's signature could be static func make(_ dependencies: DependencyTypeInputDependencyResolver) -> DependencyType).

Warning - Make sure you don't do anything unsafe with the DependencyResolver parameter passed down in this method since it won't be caught by the dependency graph validator.

- Configuration

Sets a configuration attribute to the concerned object.

Example:

// weaver: dependencyName.attributeName = aValue

@Weaver(..., attributeName: aValue, ...) 
var dependencyName: DependencyType
Configuration Attributes:

Using protperty wrappers with parameters:

Types using parameter annotations need to take the said parameters as an input when being registered or referenced. This is particularly true when using property wrappers, because the signature of the annotation won't compile if not done correctly.

For example, the following shows how a type taking two parameters at initialization can be annotated:

final class MovieViewController {

   @Weaver(.parameter) private var movieID: Int
   
   @Weaver(.parameter) private var movieTitle: String
}

And how that same type can be registered and referenced:

@WeaverP2(.registration)
private var movieViewController: (Int, String) -> MovieViewController

@WeaverP2(.reference)
private var moviewViewController: (Int, String) -> MovieViewController

Note that Weaver generates one property wrapper per amount of input parameters, so if a type takes one parameter WeaverP1 shall be used, for two parameters, WeaverP2, and so on.

Writing tests:

Weaver can also generate a dependency container stub which can be used for testing. This feature is accessible by adding the option --tests to the command (e.g. weaver swift --tests).

To compile, the stub expects certain type doubles to be implemented.

For example, given the following code:

final class MovieViewController {
   @Weaver(.reference) private var movieManager: MovieManaging
}

The generated stub expects MovieManagingDouble to be implemented in order to compile.

Testing MoviewViewController can then be written like the following:

final class MovieViewControllerTests: XCTestCase {

	func test_view_controller() {
		let dependencies = MainDependencyResolverStub()
		let viewController = dependencies.buildMovieViewController()
		
		viewController.viewDidLoad()
		
		XCTAssertEqual(dependencies.movieManagerDouble.didRequestMovies, true)
	}
}

Generate Swift Files

To generate the boilerplate code, the swift command shall be used.

$ weaver swift --help

Usage:

    $ weaver swift

Options:
    --project-path - Project's directory.
    --config-path - Configuration path.
    --main-output-path - Where the swift code gets generated.
    --tests-output-path - Where the test helpers gets generated.
    --input-path - Paths to input files.
    --ignored-path - Paths to ignore.
    --cache-path - Where the cache gets stored.
    --recursive-off
    --tests - Activates the test helpers' generation.
    --testable-imports - Modules to imports in the test helpers.
    --swiftlint-disable-all - Disables all swiftlint rules.
    --platform - Targeted platform.
    --included-imports - Included imports.
    --excluded-imports - Excluded imports.

Example:

weaver swift --project-path $PROJECT_DIR/$PROJECT_NAME --main-output-path Generated

Parameters:

Configuration File:

Weaver can read a configuration file rather than getting its parameters from the command line. It supports both json and yaml formats.

To configure Weaver with a file, write a file named .weaver.yaml or .weaver.json at the root of your project.

Parameters are named the same, but snakecased. They also work the same way with one exception, project_path cannot be defined in a configuration. Weaver automatically set its value to the configuration file location.

For example, the sample project configuration looks like:

main_output_path: Sample/Generated
input_paths:
  - Sample
ignored_paths:
  - Sample/Generated

Caching & Cleaning

In order to avoid parsing the same swift files over and over again, Weaver has a cache system built in. It means that Weaver won't reprocess files which haven't been changed since last time they got processed.

Using this functionality is great in a development environment because it makes Weaver's build phase much faster most of the time. However, on a CI it is preferable to let Weaver process the Swift files everytime for safety, for which the clean command can be used.

For example, the following always processes all of the swift code:

$ weaver clean
$ weaver swift 

Export Dependency Graph

Weaver can ouput a JSON representation of the dependency graph of a project.

$ weaver json --help
Usage:

    $ weaver json

Options:
    --project-path - Project's directory.
    --config-path - Configuration path.
    --pretty [default: false]
    --input-path - Paths to input files.
    --ignored-path - Paths to ignore.
    --cache-path - Cache path.
    --recursive-off
    --platform - Selected platform

For an output example, please check this Gist.

Migration guides

More content...

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

License

MIT license. See the LICENSE file for details.