Swift中的单例类的委托 [英] Delegation of singleton class in Swift

问题描述

如何使用单例/共享类的委托方法？
有一个单例类，其中定义了一些协议，但是我没有获得如何访问其他类中的委托函数的方法。

How to use delegate methods of singleton/shared class? There is one singleton class having some protocol defined but I'm not getting how to access the delegate functions in other classes.

代码段供参考（迅速）：

Code snippet for a reference (swift):

protocol AClassDelegate
{
  func method1()
}

class A
{
   static let shared = A()

   override init() {
     //initialisation of member variables
   }

   var delegate: AClassDelegate
   func foo() {

   }
}


class B: AClassDelegate
{
   func bar() {
      // Note: not getting call to 'foo' method of class 'A'
      A.shared.delegate = self
      A.shared.foo()
   }
}

此实现正确吗？

推荐答案

首先，我想指向：

1-创建单例类应包含：

private init() {}

强制仅通过使用其共享实例访问该类。

That leads to enforce to access the class only by using its shared instance.

2-如 Max的答案，委托应该是可选的，并且具有弱引用。

2- As mentioned in Max's Answer, the delegate should be optional and has a weak reference.

3-协议应为 class 类型，如下所示：

3- The protocol should be a type of class, as follows:

protocol AClassDelegate: class

有关更多信息，您可能需要检查此问题与解答。

现在，为了进行测试，我们假设 method1（）在 foo（）时应调用 AClassDelegate 中的 > A 类：

Now, let's assume -for testing purposes- that the method1() from AClassDelegate should be get called when calling foo() from A class:

protocol AClassDelegate: class {
    func method1()
}

class A {
    private init() {}
    static let shared = A()

    weak var delegate: AClassDelegate?

    func foo() {
        print(#function)

        delegate?.method1()
    }
}

让我们的实现类符合 AClassDelegate ：

class B: AClassDelegate {
    func bar() {
        A.shared.delegate = self
        A.shared.foo()
    }

    func method1() {
        print("calling the delegate method B Class")
    }
}

class C: AClassDelegate {
    func bar() {
        A.shared.delegate = self
        A.shared.foo()
    }

    func method1() {
        print("calling the delegate method C Class")
    }
}

输出应为：

let b = B()
b.bar()
// this will print:
/*
 foo()
 calling the delegate method B Class
 */

let c = C()
c.bar()
// this will print:
/*
 foo()
 calling the delegate method C Class
 */

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