Learning from Open Source Generic Factory

Issue #148

From https://github.com/devxoul/Pure/blob/master/Sources/Pure/FactoryModule.swift

public protocol FactoryModule: Module {

  /// A factory for `Self`.
  associatedtype Factory = Pure.Factory<Self>

  /// Creates an instance of a module with a dependency and a payload.
  init(dependency: Dependency, payload: Payload)
}

From https://github.com/devxoul/Pure/blob/master/Sources/Pure/Factory.swift

open class Factory<Module: FactoryModule> {
  private let dependencyClosure: () -> Module.Dependency

  /// A static dependency of a module.
  open var dependency: Module.Dependency {
    return self.dependencyClosure()
  }

  /// Creates an instance of `Factory`.
  ///
  /// - parameter dependency: A static dependency which should be resolved in a composition root.
  public init(dependency: @autoclosure @escaping () -> Module.Dependency) {
    self.dependencyClosure = dependency
  }

  /// Creates an instance of a module with a runtime parameter.
  ///
  /// - parameter payload: A runtime parameter which is required to construct a module.
  open func create(payload: Module.Payload) -> Module {
    return Module.init(dependency: self.dependency, payload: payload)
  }
}

From https://github.com/devxoul/Pure/blob/master/Tests/PureTests/PureSpec.swift#L72

let factory = FactoryFixture<Dependency, Payload>.Factory(dependency: .init(
  networking: "Networking A"
))
let instance = factory.create(payload: .init(id: 100))
expect(instance.dependency.networking) == "Networking A"
expect(instance.payload.id) == 100