Html parsing 如何使用两个块作为参数的方法，第一个块有一个返回值，第二个块需要获取返回值

我的项目中的源代码如下所示

 -(id)init:(NSString *)url
        withParseBlock:(htmlParseBlock)parseBlock
        andResultBlock:(ItemsReturnBlock)resultBlock
   {
    self = [super init];
    if(self!=nil){

         [_parseBlock release];
        _parseBlock = [parseBlock copy];

        [_returnBlock release];
        _returnBlock = [resultBlock copy];

        _asiRequest = [[ASIHTTPRequest alloc ] initWithURL:[NSURL URLWithString:url]];

        __block HttpParseSession * self_ = self;
      dispatch_queue_t httpQueue =    dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, nil);
        dispatch_block_t block = ^{
            @autoreleasepool {
                 [self_ start];
            }
        };
        if(dispatch_get_current_queue()==httpQueue){
            block();
        }else{
            dispatch_async(httpQueue, block);
        }


    }
    return self;

}

第一个块返回一个对象，第二个块需要将该对象作为参数传入

 [kNetManagerInstance exeHttpRequest:anUrl requestFrom:self withParseBlock:^id(NSData       *htmlData) {
        NSMutableArray *arr = doSomeParsingWorkOn(htmlData); 

        return arr; //return the html parsed result for the seconde block to use.

    } andResultBlock:^(id object) {


        NSLog(@"%@",object);//can output the object but
        //crash  when execute out of the scope,EXC_BAD_ACCESS(code=2,address=0xc)  
    }]; 

上面的方法做的事情如下

 -(id)init:(NSString *)url
        withParseBlock:(htmlParseBlock)parseBlock
        andResultBlock:(ItemsReturnBlock)resultBlock
   {
    self = [super init];
    if(self!=nil){

         [_parseBlock release];
        _parseBlock = [parseBlock copy];

        [_returnBlock release];
        _returnBlock = [resultBlock copy];

        _asiRequest = [[ASIHTTPRequest alloc ] initWithURL:[NSURL URLWithString:url]];

        __block HttpParseSession * self_ = self;
      dispatch_queue_t httpQueue =    dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, nil);
        dispatch_block_t block = ^{
            @autoreleasepool {
                 [self_ start];
            }
        };
        if(dispatch_get_current_queue()==httpQueue){
            block();
        }else{
            dispatch_async(httpQueue, block);
        }


    }
    return self;

}

在httpQueue中调用的方法
-（无效）开始{