如何从另一个类中的一个类调用方法（iOS）

How to call method from one class in another (iOS)

提问by Matt Ledger

This a very basic question but I've searched all over and been unable to find an answer that explains well enough for me to get my head around it.

这是一个非常基本的问题，但我已经搜索了所有内容，但无法找到一个解释得足够好让我理解它的答案。

What I want to do is create a method in one class of my iOS app and then call that method from other classes in my app. Could someone explain exactly what I need to do to achieve this? Any help would be greatly appreciated as all my attempts so far have failed!

我想要做的是在我的 iOS 应用程序的一个类中创建一个方法，然后从我的应用程序中的其他类调用该方法。有人可以确切地解释我需要做什么来实现这一目标吗？任何帮助将不胜感激，因为到目前为止我所有的尝试都失败了！

Thanks.

谢谢。

回答by Pochi

Objective-C:

目标-C：

You have to import the header of the class that contains the method you want to use (ClassYouWantToUse.h) into the class you want to use it at (TargetClass).

您必须将包含要使用的方法的类的标头 ( ClassYouWantToUse.h) 导入到要在 ( TargetClass)使用它的类中。

Inside the TargetClass.h or TargetClass.m (depending on the scope you want to give it):

在 TargetClass.h 或 TargetClass.m 中（取决于你想给它的范围）：

#import "ClassYouWantToUse.h"

Then create an instance of the class you want to use inside the target class either as a property like this:

然后创建一个你想在目标类中使用的类的实例，作为这样的属性：

@property (nonatomic,strong) ClassYouWantToUse *classObject;

Or as an instance variable like this:

或者作为这样的实例变量：

ClassYouWantToUse *classObject;

Make sure you initialize it! (usually inside ViewDidLoad):

确保你初始化它！（通常在 ViewDidLoad 中）：

classObject = [[ClassYouWantToUse alloc] init];

Now you can call any public methods from that class like this:

现在您可以像这样从该类调用任何公共方法：

[classObject theClassMethodWithParam:param1 andSecondParam:param2];

Note:The ClassYouWantToUse class must have the methods that you want to make accessible to others by declaring them in the header file:

注意：ClassYouWantToUse 类必须具有您希望通过在头文件中声明其他人可以访问的方法：

- (void)theClassMethodWithParam:(UIImage*)someImage andSecondParam:(NSString*)someText;

Otherwise you won't be able to see these methods.

否则，您将无法看到这些方法。

---

---

Swift:

迅速：

Theres really nothing special about it in swift, just adding this as a reference.

在 swift 中确实没有什么特别之处，只是将其添加为参考。

In swift you simply create an instance of the class you want to use:

在 swift 中，您只需创建要使用的类的实例：

let classObject = ClassYouWantToUse()

And use it directly:

并直接使用它：

classObject.theClassMethodWithParam(param1, andSecondParam:param2)

回答by aroth

You have two basic options. You can either create or pass-in an instance of the first class to the second class, or you can add a static method to the first class and call it directly using the class object.

您有两个基本选项。您可以创建或将第一个类的实例传递给第二个类，也可以向第一个类添加静态方法并使用类对象直接调用它。

For instance, say you have:

例如，假设您有：

@interface ClassA : NSObject {
}

//instance methods
- (int) addNumber:(int)num1 withNumber:(int)num2;

//static/class methods
+ (int) add:(int)num1 with:(int)num2;
@end

@implementation ClassA
- (int) addNumber:(int)num1 withNumber:(int)num2 {
    return num1 + num2;
}

+ (int) add:(int)num1 with:(int)num2 {
    return num1 + num2;
}
@end

Then you can do:

然后你可以这样做：

#import "ClassA.h"

@interface ClassB : NSObject {
    ClassA* adder;
}

//constructors
- (id) init;  //creates a new instance of ClassA to use
- (id) initWithAdder:(ClassA*)theAdder;  //uses the provided instance of ClassA

//instance methods
- (int) add2To:(int)num;

//static/class methods
+ (int) add3To:(int)num;
@end

@implementation ClassB
- (id) init {
    if (self = [super init]) {
        adder = [[ClassA alloc] init];
    }
    return self;
}

- (id) initWithAdder:(ClassA*)theAdder {
    if (self = [super init]) {
        adder = theAdder;
    }
    return self;
}

- (int) add2To:(int)num {
    return [adder addNumber:2 withNumber:num];
}

+ (int) add3To:(int)num {
    return [ClassA add:3 with:num];
}
@end

Note that in most cases, you would use instance methods rather than static methods.

请注意，在大多数情况下，您将使用实例方法而不是静态方法。

回答by anticyclope

You have to use the concept of delegation.

您必须使用委托的概念。

https://developer.apple.com/library/ios/#documentation/General/Conceptual/CocoaEncyclopedia/DelegatesandDataSources/DelegatesandDataSources.html

https://developer.apple.com/library/ios/#documentation/General/Conceptual/CocoaEncyclopedia/DelegatesandDataSources/DelegatesandDataSources.html