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

我是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的说法-

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

关于我所缺少的任何想法吗？

我个人认为，更符合您需求的解决方案是使用NSInvocation。

类似于以下内容的工作：

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];
}

因为没有这样的东西 [NSObject performSelector:withObject:withObject:afterDelay:]方法。

您需要将要发送的数据封装到某个单一的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:]众所周知方法。

例如：

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

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

您可以将参数打包到一个对象中，并使用一个助手方法来调用您的原始方法，就像迈克尔和其他人建议的那样。

另一个选项是dispatch_after，它将采用一个块并在特定时间将其排入队列。

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，则可以使用 - performSelector:withObject:withObject:

最简单的选择是将方法修改为采用包含两个参数的单个参数，例如NSArrayor或NSDictionary（或添加采用单个参数的第二个方法，将其解压缩，然后调用第一个方法，然后调用第二个方法上的方法延迟）。

例如，您可能会遇到以下情况：

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

然后调用它，您可以执行以下操作：

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

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


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

}

并调用：

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

您可以在此处找到所提供的performSelector：方法的所有类型：

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

有很多变化，但是没有一个版本可以同时包含多个对象和一个延迟。您需要将参数包装在NSArray或NSDictionary中。

- 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: 

我不喜欢NSInvocation的方式，太复杂了。让我们保持简洁：

// Assume we have these variables
id target, SEL aSelector, id parameter1, id parameter2;

// Get the method IMP, method is a function pointer here.
id (*method)(id, SEL, id, id) = (void *)[target methodForSelector:aSelector];

// IMP is just a C function, so we can call it directly.
id returnValue = method(target, aSelector, parameter1, parameter2);

我只是做了一些麻烦，需要调用原始方法。我所做的就是制定一个协议，并将我的对象投向它。另一种方法是在类别中定义方法，但需要禁止显示警告（#pragma clang诊断忽略“ -Wincomplete-implementation”）。

一种简单且可重用的方法是扩展NSObject和实现

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

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; //0 and 1 reserved
    for (NSObject *argument in arguments) {
        [invocation setArgument: &argument atIndex: index];
        index ++;
    }
    [invocation invokeWithTarget: self];
}

我只是创建一个将所有参数都保存为属性的自定义对象，然后将该单个对象用作参数