iOS - 如何使用多个参数和afterDelay实现performSelector？

Question

我是一个iOS新手.我有一个选择器方法如下 -

- (void) fooFirstInput:(NSString*) first secondInput:(NSString*) second
{

}

我正在尝试实现这样的东西 -

[self performSelector:@selector(fooFirstInput:secondInput:) withObject:@"first" withObject:@"second" afterDelay:15.0];

但这给了我一个错误说 -

Instance method -performSelector:withObject:withObject:afterDelay: not found

关于我缺少什么的任何想法？

Answer 1

就个人而言,我认为更接近您的需求的解决方案是使用NSInvocation.

像下面这样的东西会做的工作:

indexPath和 dataSource是在同一方法中定义的两个实例变量.

SEL aSelector = NSSelectorFromString(@"dropDownSelectedRow:withDataSource:");

if([dropDownDelegate respondsToSelector:aSelector]) {
    NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[dropDownDelegate methodSignatureForSelector:aSelector]];
    [inv setSelector:aSelector];
    [inv setTarget:dropDownDelegate];

    [inv setArgument:&(indexPath) atIndex:2]; //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation
    [inv setArgument:&(dataSource) atIndex:3]; //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation

    [inv invoke];
}

Answer 2

因为没有[NSObject performSelector:withObject:withObject:afterDelay:]方法这样的东西.

您需要将要发送的数据封装到单个Objective C对象(例如NSArray,NSDictionary,某些自定义Objective C类型)中,然后将其传递给[NSObject performSelector:withObject:afterDelay:]众所周知和喜爱的方法.

例如:

NSArray * arrayOfThingsIWantToPassAlong = 
    [NSArray arrayWithObjects: @"first", @"second", nil];

[self performSelector:@selector(fooFirstInput:) 
           withObject:arrayOfThingsIWantToPassAlong  
           afterDelay:15.0];

Answer 3

您可以将参数打包到一个对象中,并使用辅助方法将原始方法称为Michael,现在其他人已建议.

另一个选项是dispatch_after,它将占用一个块并在某个时间将其入队.

double delayInSeconds = 15.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);

dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

    [self fooFirstInput:first secondInput:second];

});

或者,正如您已经发现的那样,如果您不需要延迟,您可以使用 - performSelector:withObject:withObject:

Answer 4

最简单的选择是修改你的方法以获取包含两个参数的单个参数,例如NSArray或NSDictionary(或者添加第二个接受单个参数的方法,解压缩它,调用第一个方法,然后调用第二个方法)延迟).

例如,你可以有类似的东西:

- (void) fooOneInput:(NSDictionary*) params {
    NSString* param1 = [params objectForKey:@"firstParam"];
    NSString* param2 = [params objectForKey:@"secondParam"];
    [self fooFirstInput:param1 secondInput:param2];
}

然后打电话给你,你可以这样做:

[self performSelector:@selector(fooOneInput:) 
      withObject:[NSDictionary dictionaryWithObjectsAndKeys: @"first", @"firstParam", @"second", @"secondParam", nil] 
      afterDelay:15.0];

Answer 5

- (void) callFooWithArray: (NSArray *) inputArray
{
    [self fooFirstInput: [inputArray objectAtIndex:0] secondInput: [inputArray objectAtIndex:1]];
}


- (void) fooFirstInput:(NSString*) first secondInput:(NSString*) second
{

}

并称之为:

[self performSelector:@selector(callFooWithArray) withObject:[NSArray arrayWithObjects:@"first", @"second", nil] afterDelay:15.0];

Answer 6

你可以在这里找到提供的所有类型的performSelector:方法:

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/nsobject_Class/Reference/Reference.html

有许多变化,但没有一个版本需要多个对象以及延迟.您需要在NSArray或NSDictionary中包装您的参数.

- performSelector:
- performSelector:withObject:
- performSelector:withObject:withObject:
– performSelector:withObject:afterDelay:
– performSelector:withObject:afterDelay:inModes:
– performSelectorOnMainThread:withObject:waitUntilDone:
– performSelectorOnMainThread:withObject:waitUntilDone:modes:
– performSelector:onThread:withObject:waitUntilDone:
– performSelector:onThread:withObject:waitUntilDone:modes:
– performSelectorInBackground:withObject: