Question

我正在尝试使用从另一个NSOperation

开始的NSOperation

这是最内在的NSOperation：

         #pragma mark - OVERRIDE

        - (void)main
        {
            @autoreleasepool {

                if (self.isCancelled) {
                    return;
                }

                NSURL *url = [NSURL URLWithString:self.urlStr];
                NSURLRequest *request = [NSURLRequest requestWithURL:url];
                self.urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
            }
        }

        #pragma mark - NSURLConnectionDataDelegate

        - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
        {
// NEVER CALLED
            if (self.isCancelled) {
                [connection cancel];
                self.receivedData = nil;
                return;
            }
            [self.receivedData appendData:data];
        }

        - (void)connectionDidFinishLoading:(NSURLConnection *)connection
        {// NEVER CALLED
            if (self.isCancelled) {
                self.receivedData = nil;
                return;
            }
            // return data to the delegate 
    }

问题是虽然main方法被称为didReceiveData neverGetsCalled。

我在这里开始这个操作：

- (void)main
{
    @autoreleasepool {
        if (self.isCancelled) {
            return;
        }
        NSOperationGetJSONFromWeb *webGetOp = [[NSOperationGetJSONFromWeb alloc] initWithURLString:self.urlStr andDelegate:self];
        [self.opQueue addOperation:webGetOp];
    }
}

这显然来自另一个NSOperation。这里有什么问题？如果我直接调用此操作（而不是从另一个操作），一切正常。

Answer 1

使用KVO标志，如

   #pragma mark - OVERRIDE

    - (void)main
    {
        @autoreleasepool {

            if (self.isCancelled) {
                return;
            }

            NSURL *url = [NSURL URLWithString:self.urlStr];
            NSURLRequest *request = [NSURLRequest requestWithURL:url];
            [self willChangeValueForKey:@"isExecuting"];
            self.urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
            executing = YES;
            [self didChangeValueForKey:@"isExecuting"];
        }
    }

    #pragma mark - NSURLConnectionDataDelegate

    - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
    {
       // NEVER CALLED
        if (self.isCancelled) {
            [connection cancel];
            self.receivedData = nil;
            return;
        }
        [self.receivedData appendData:data];
    }

    - (void)connectionDidFinishLoading:(NSURLConnection *)connection
    {// NEVER CALLED

        [self willChangeValueForKey:@"isFinished"];
        [self willChangeValueForKey:@"isExecuting"];

         executing = NO;
         finished = YES;

        [self didChangeValueForKey:@"isExecuting"];
        [self didChangeValueForKey:@"isFinished"];
        if (self.isCancelled) {
            self.receivedData = nil;
            return;
        }
        // return data to the delegate 
}

NSOperation未能完成

1 个答案: