Bridge を Swift で

import XCTest /// The Abstraction defines the interface for the "control" part of the two /// class hierarchies. It holds a reference to an object from the Implementation /// hierarchy and delegates all of the real work to this object. class Abstraction { fileprivate var implementation: Implementation init(_ implementation: Implementation) { self.implementation = implementation } func operation() -> String { let operation = implementation.operationImplementation() return "Abstraction: Base operation with:\n" + operation } } /// You can extend the Abstraction without changing the Implementation classes. class ExtendedAbstraction: Abstraction { override func operation() -> String { let operation = implementation.operationImplementation() return "ExtendedAbstraction: Extended operation with:\n" + operation } } /// The Implementation defines the interface for all implementation classes. It /// doesn't have to match the Abstraction's interface. In fact, the two /// interfaces can be entirely different. Typically the Implementation interface /// provides only primitive operations, while the Abstraction defines higher- /// level operations based on those primitives. protocol Implementation { func operationImplementation() -> String } /// Each Concrete Implementation corresponds to a specific platform and /// implements the Implementation interface using that platform's API. class ConcreteImplementationA: Implementation { func operationImplementation() -> String { return "ConcreteImplementationA: Here's the result on the platform A.\n" } } class ConcreteImplementationB: Implementation { func operationImplementation() -> String { return "ConcreteImplementationB: Here's the result on the platform B\n" } } /// Except for the initialization phase, where an Abstraction object gets linked /// with a specific Implementation object, the client code should only depend on /// the Abstraction class. This way the client code can support any abstraction- /// implementation combination. class Client { // ... static func someClientCode(abstraction: Abstraction) { print(abstraction.operation()) } // ... } /// Let's see how it all works together. class BridgeConceptual: XCTestCase { func testBridgeConceptual() { // The client code should be able to work with any pre-configured // abstraction-implementation combination. let implementation = ConcreteImplementationA() Client.someClientCode(abstraction: Abstraction(implementation)) let concreteImplementation = ConcreteImplementationB() Client.someClientCode(abstraction: ExtendedAbstraction(concreteImplementation)) } } 

Abstraction: Base operation with: ConcreteImplementationA: Here's the result on the platform A ExtendedAbstraction: Extended operation with: ConcreteImplementationB: Here's the result on the platform B