从另一个类调用委托方法 [英] Call Delegate methods from another class
问题描述
我无法弄清楚如何在 C# 中编写跨类的委托方法调用.我来自 Objective-C 的世界,这可能让我感到困惑.在 Objective-C 中,我可以在子类中分配一个委托对象作为父类(即,childViewcontroller.delegate = self;
).然后我可以使用以下方法在委托类中触发一个方法:
I am having trouble figuring out how to program delegate method calls across classes in C#. I am coming from the world of Objective-C, which may be confusing me. In Objective-C, I can assign a delegate object inside a child class, to be the parent class (I.e., childViewcontroller.delegate = self;
). Then I can to fire a method in the delegate class by using:
if([delegate respondsToSelector:@selector(methodName:)]) {
[delegate methodName:parametersgohere];
}
但是,我不知道如何在 C# 中执行此操作.我已经阅读了一些关于 C# 委托的一般内容(例如,在这里),但我还是卡住了.
However, I can't figure out how to do this in C#. I've read a bit about C# delegates in general (for example, here), but I'm still stuck.
有什么例子可以解释这个吗?
Are there any examples that explain this?
这是我的完整场景:我有 classA 实例化 classB 的实例.ClassB 触发一个方法(调用 Web 服务),在响应时,我想触发 classA 中的方法.
Here is my scenario in full: I have classA which instantiates an instance of classB. ClassB fires a method (which call a web service), and upon response, I'd like to fire a method in classA.
是否有任何Hello World"类型的教程可以解释这方面的基础知识?
Any 'Hello World' types of tutorials out there that might explain the very basics of this?
推荐答案
委托是指向方法的对象,无论是静态方法还是实例方法.因此,对于您的示例,您只需使用事件模型:
A delegate is an object that points to a method, be it a static or instance method. So for your example, you would just use the event model:
class Caller {
public void Call() {
new Callee().DoSomething(this.Callback); // Pass in a delegate of this instance
}
public void Callback() {
Console.WriteLine("Callback called!");
}
}
class Callee {
public void DoSomething(Action callback) {
// Do stuff
callback(); // Call the callback
}
}
...
new Caller().Call(); // Callback called!
Caller
实例将委托传递给 Callee
实例的 DoSomething
方法,后者又调用指向的方法,即Caller
实例的Callback
方法.
The Caller
instance passes a delegate to the Callee
instance's DoSomething
method, which in turn calls the pointed-to method, which is the Callback
method of the Caller
instance.
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