iphone - 尝试将 NSData 从 NSURLConnection 写入文件后的 SIGABRT(无法识别的选择器)

Question

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已解决:文件名是一个自动释放的字符串，在调用 createFileAtPath 时不再可用:

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我正在尝试跟踪文件的下载进度，我正在尝试实现的代码是这样的(已编辑):

 connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];

    if (connection)
        receivedData = [[NSMutableData data] retain];    

    -(void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [receivedData setLength:0];

    totalBytes = [[NSNumber numberWithLongLong:[response expectedContentLength]] intValue];
    NSLog(@"content-length: %i bytes", totalBytes);
}

-(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [receivedData appendData:data];

    int resourceLength = [[NSNumber numberWithUnsignedInteger:[receivedData length]] intValue];
    NSLog(@"receivedData length: %i", resourceLength);
}

-(void) connectionDidFinishLoading:(NSURLConnection *)connection
{
    [fileMgr createFileAtPath:filename contents:receivedData attributes:nil];

    //if instead i write only the Apple example:
    //NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]);
    //there's no SIGABRT
    [receivedData release];
    [connection release];
}

但是 createFileAtPath:contents:attributes: 只给出 SIGABRT:

-[__NSCFData getFileSystemRepresentation:maxLength:]: unrecognized selector sent to instance 0x2ba510

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFData getFileSystemRepresentation:maxLength:]: unrecognized selector sent to instance 0x2ba510'

我做错了什么？这不是异步下载文件的方式吗？

还有 2 件事:a) 内容长度 NSLog 是正确的。 b) 如果我不在 didReceiveResponse 中使用 initWithCapacity:content-lenght 而只是初始化，则 receivedData 长度只会增长大约内容长度的两倍...

Answer 1

已解决:文件名是一个自动释放的字符串，在调用 createFileAtPath 时不再可用: