ios – 如何在这个块中强力地修复“捕获”块可能导致保留周期“

我正在处理这个代码,它在网络上做了一些冗长的异步操作,当它完成它触发完成块时,执行一些测试,如果一个变量获得一定值,另一个冗长的操作应该立即开始：

-(void) performOperation
{

    void(^completionBlock) (id obj,NSError *err,NSURLRequest *request)= ^(id obj,NSURLRequest *request){


        int variable=0;

        // Do completion operation A
        //...
        //...

        // Do completion operation B                
        //Get the variable value

        if(variable>0){
            [self doLengthyAsynchronousOperationWithCompletionBlock: completionBlock];
        }

    };

//Perform the lenhgty operation with the above completionBlock
    [self doLengthyAsynchronousOperationWithCompletionBlock: completionBlock];

}

-(void) doLengthyAsynchronousOperationWithCompletionBlock: completionBlock
{
    //Do some lengthy asynchronous stuff
}

有了这个代码,我从编译器得到这个警告：

WARNING: Block pointer variable 'completionBlock' is uninitialized when caputerd by the block

我变了：

void(^completionBlock) (id obj,NSURLRequest *request)

在：

__block void(^completionBlock) (id obj,NSURLRequest *request)

但我得到这个其他警告：

WARNING 2: Capturing 'completionBlock' strongly in this block is likely to lead to a retain cycle

如何解决这个问题？

谢谢

尼古拉

    void(^ completionBlock) (id obj,NSURLRequest *request);
    void(^ __block __weak weakCompletionBlock) (id obj,NSURLRequest *request);
    weakCompletionBlock = completionBlock = ^(id obj,NSURLRequest *request){
        [self lengthyAsyncMethod:weakCompletionBlock];
    };