@selector 中的参数 [英] Arguments in @selector

问题描述

有什么办法可以在选择器中传递参数吗?

Is there any way that I can pass arguments in selector?

示例:我有这个方法

- (void)myMethod:(NSString*)value1 setValue2:(NSString*)value2{

}

我需要通过传递两个参数的选择器来调用这个函数.

and I need to call this function through a selector passing two arguments.

[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(/*my method*/) userInfo:nil repeats:YES];

我该怎么做?

推荐答案

你可以使用 NSTimer 方法:

+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)seconds
                                 invocation:(NSInvocation *)invocation
                                    repeats:(BOOL)repeats;

相反，由于 NSInvocation 对象将允许您传递参数；NSInvocation 对象是，作为 docs 定义它:

Instead, since an NSInvocation object will allow you to pass arguments; an NSInvocation object is, as the docs define it:

Objective-C 消息呈现静态，也就是说，它是一个动作变成了一个对象.

an Objective-C message rendered static, that is, it is an action turned into an object.

虽然使用选择器创建 NSTimer 对象需要方法的格式是:

Whilst creating an NSTimer object using a selector requires the format of the method being:

- (void)timerFireMethod:(NSTimer*)theTimer

NSInvocation 允许您设置目标、选择器和传入的参数:

An NSInvocation allows you to set the target, the selector, and the arguments that you pass in:

SEL selector = @selector(myMethod:setValue2:);

NSMethodSignature *signature = [MyObject instanceMethodSignatureForSelector:selector];
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
[invocation setSelector:selector];

NSString *str1 = @"someString";
NSString *str2 = @"someOtherString";

//The invocation object must retain its arguments
[str1 retain];
[str2 retain];

//Set the arguments
[invocation setTarget:targetInstance];
[invocation setArgument:&str1 atIndex:2];
[invocation setArgument:&str2 atIndex:3];

[NSTimer scheduledTimerWithTimeInterval:0.1 invocation:invocation repeats:YES];

其中 MyObject 是在其上声明和实现 myMethod:setValue2: 的类 – instanceMethodSignatureForSelector: 是在 NSObject 返回一个 NSMethodSignature 对象，传递给 NSInvocation.

Where MyObject is the class that myMethod:setValue2: is declared and implemented on – instanceMethodSignatureForSelector: is a convenience function declared on NSObject which returns an NSMethodSignature object for you, to be passed to NSInvocation.

另外，请注意，使用 setArgument:atIndex:，要传递给设置为选择器的方法的参数的索引从索引 2 开始.来自文档:

Also, to note, with setArgument:atIndex:, the indices for arguments to be passed to the method set as the selector start at index 2. From the docs:

索引0和1分别表示隐藏参数self和_cmd；您应该直接使用 setTarget: 和 setSelector: 方法设置这些值.对通常在消息中传递的参数使用索引 2 和更大的索引.

Indices 0 and 1 indicate the hidden arguments self and _cmd, respectively; you should set these values directly with the setTarget: and setSelector: methods. Use indices 2 and greater for the arguments normally passed in a message.

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