使用NSOperation时未捕获的异常：performSelector：

Question

我试图为我的NSOperation添加一个选择器，但它给了我：

-[NSOperation sample]: unrecognized selector sent to instance 0x17e35830
2014-11-06 20:03:26.542 ****[1473:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSOperation sample]: unrecognized selector sent to instance 0x17e35830'
*** First throw call stack:
(0x303d8f53 0x3aa416af 0x303dc8e7 0x303db1d3 0x3032a598 0x820d5 0xa457d 0x590b9 0x3af24d7b 0x3af24d67 0x3af2b7c1 0x303a3821 0x303a20f5 0x3030cce7 0x3030cacb 0x34fda283 0x32baea41 0x78339 0x3af49ab7)
libc++abi.dylib: terminating with uncaught exception of type NSException

我的代码：

NSOperation *op = [[NSOperation alloc] init];
[op performSelector:@selector(sample)];
[MyQueue addOperation:op];

- (void)sample{
  NSLog(@"sample");
}

Answer 1

问题正是错误所说的，NSOperation没有名为sample的方法。您可以通过[self sample];或[self performSelector:@selector(sample)];

在此处拨打电话

Answer 2

我刚刚使用NSInvocationOperation作为NSOperation的子类，我认为最好在指定对象上调用一个选择器。

苹果：

The NSInvocationOperation class is a concrete subclass of NSOperation that manages the 
execution of a single encapsulated task specified as an invocation.You can use this 
class to initiate an operation that consists of invoking a selector on 
a specified object. This class implements a non-concurrent operation.

示例代码：

NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(sample) object:nil];

Answer 3

以这种方式尝试：

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSOperationQueue *operationQueue=[NSOperationQueue new];

    NSInvocationOperation *operation=[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(changeText) object:nil];
    [operationQueue addOperation:operation];
}

-(void)changeText{
    ........
    ..........
    ...........
}