objective-c @selector - 有多个参数？

@selector - With Multiple Arguments?

提问by fuzzygoat

I have been using @selectortoday for the first time and have not been able to work out how to do the following? How would you write the @selectorif you had more than one argument?

我@selector今天第一次使用，一直无法解决以下问题？@selector如果你有不止一个论点，你会怎么写？

No arguments:

没有论据：

-(void)printText {
    NSLog(@"Fish");
}

[self performSelector:@selector(printText) withObject:nil afterDelay:0.25];

Single argument:

单一参数：

-(void)printText:(NSString *)myText {
    NSLog(@"Text = %@", myText);
}

[self performSelector:@selector(printText:) withObject:@"Cake" afterDelay:0.25];

Two arguments:

两个论点：

-(void)printText:(NSString *)myText andMore:(NSString *)extraText {
    NSLog(@"Text = %@ and %@", myText, extraText);
}

[self performSelector:@selector(printText:andMore:) withObject:@"Cake" withObject:@"Chips"];

Multiple Arguments: (i.e. more than 2)

多个参数：（即超过 2 个）

NSInvocation

NSInvocation

回答by cobbal

 

 

 - (id)performSelector:(SEL)aSelector
           withObject:(id)anObject  
           withObject:(id)anotherObject

From the Documentation:

从文档：

This method is the same as performSelector:except that you can supply two arguments for aSelector. aSelector should identify a method that can take two arguments of type id. For methods with other argument types and return values, use NSInvocation.

此方法与performSelector相同：除了您可以为 aSelector 提供两个参数。aSelector 应该标识一个可以接受两个 id 类型参数的方法。对于具有其他参数类型和返回值的方法，请使用NSInvocation。

so in your case you would use:

所以在你的情况下，你会使用：

[self performSelector:@selector(printText:andMore:)
           withObject:@"Cake"
           withObject:@"More Cake"]

回答by Yoav

As an alternative for NSInvocation when you have more than two parameters, you can use NSObject's -methodForSelector:as in the following example:

当您有两个以上的参数时，作为 NSInvocation 的替代方案，您可以使用 NSObject 的-methodForSelector:如下例所示：

SEL a_selector = ...
Type1 obj1 = ...
Type2 obj2 = ...
Type3 obj3 = ...
typedef void (*MethodType)(id, SEL, Type1, Type2, Type3);
MethodType methodToCall;
methodToCall = (MethodType)[target methodForSelector:a_selector];
methodToCall(target, a_selector, obj1, obj_of_type2, obj_of_type3);

回答by aqua

I had an issue where I needed to use the afterDelayalong with multiple arguments to my @selectormethod. Solution? Use a wrapper function!

我遇到了一个问题，我需要afterDelay在我的@selector方法中使用和多个参数。解决方案？使用包装函数！

Say this is the function I wantto pass to @selector:

说这是我想传递给的函数@selector：

-(void)myFunct:(NSString *)arg1 andArg:(NSString *)arg2 andYetAnotherArg:(NSString *)arg3;

Obviously, I can't even use withObject: withObject:here, so, make a wrapper!

显然，我什至不能withObject: withObject:在这里使用，所以，做一个包装！

-(void)myFunctWrapper:(NSArray *)myArgs {
    [self myFunct:[myArgs objectAtIndex:0] andArg:[myArgs objectAtIndex:1] andYetAnotherArg:[myArgs objectAtIndex:2]];
}

and use it by doing:

并通过以下方式使用它：

NSArray *argArray = [NSArray arrayWithObjects:string1,string2,string3,nil];
[self performSelector:@selector(myFunctWrapper:) withObject:argArray afterDelay:1.0];

This way I can have multiple arguments anduse the selector with delay.

这样我就可以有多个参数并延迟使用选择器。

回答by kennytm

@selector(printText:andMore:)

回答by pheelicks

[self performSelector:@selector(printText:andMore) withObject:@"Cake" withObject:@"More Cake"];

回答by Yoav

Another option is to use an even shorter syntax:

另一种选择是使用更短的语法：

#import <objc/message.h> // objc_msgSend
...
((void (*)(id, SEL, Type1, Type2, Type3))objc_msgSend)(target, a_selector, obj1, obj_of_type2, obj_of_type3);

回答by fphilipe

Elaborating on Ben-Uri's answer, which can be written way shorter.

详细说明Ben-Uri 的答案，可以写得更短。

E.g. calling the UIViewmethod - (CGPoint)convertPoint:(CGPoint)point toView:(UIView *)viewcan be done as follows:

例如调用该UIView方法- (CGPoint)convertPoint:(CGPoint)point toView:(UIView *)view可以如下完成：

SEL selector = @selector(covertPoint:toView:);
IMP method = [viewA methodForSelector:selector];
CGPoint pointInB = method(viewA, selector, pointInA, viewB);

回答by VoidPointer

As KennyTM pointed out, the selector syntax is

正如 KennyTM 指出的，选择器语法是

@selector(printText:andMore:)

You call it with

你用

performSelector:withObject:withObject. 

... if you need more arguments or different types, you need to use NSIvocation

...如果你需要更多的参数或不同的类型，你需要使用NSIvocation

回答by Kappe

Using NSInvocationas you specify you can create an NSObject category that implements

在指定时使用NSInvocation可以创建一个 NSObject 类别来实现

- (void)performSelector:(SEL)aSelector withObjects:(NSArray *)arguments;

Something like:

就像是：

- (void)performSelector:(SEL)aSelector withObjects:(NSArray *)arguments
{
    NSMethodSignature *signature = [self methodSignatureForSelector: aSelector];
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature: signature];
    [invocation setSelector: aSelector];

    int index = 2; //
    for (NSObject *argument in arguments) {
        [invocation setArgument: &argument atIndex: index];
        index ++;
    }
    [invocation invokeWithTarget: self];
}

from: iOS - How to implement a performSelector with multiple arguments and with afterDelay?

来自：iOS - 如何实现具有多个参数和 afterDelay 的 performSelector？