'NSString'没有可见的@interface声明选择器'appendData'

Question

我试图异步调用服务器（ARC -on）：

NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:request delegate:self];

if (theConnection) {
    content = [NSMutableData data];
    NSLog(@"responseData from setup.php: %@", content);
} else {        
    // Inform the user that the connection failed.
    NSLog(@"error from server response in set up");
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"connection did receive response");
}

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

    NSLog(@"connection did receive data");
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
   NSLog(@"connection did finish load");
   NSLog(@"Succeeded! Received %@ bytes of data",receivedData);
}

但是我从服务器获取内容时遇到问题：-在didReceiveData函数中，出现以下错误：-'NSString'没有可见的@interface声明选择器'appendData'

有人可以建议我哪里我错了吗？

Answer 1

在接口部分的.h文件中，请声明以下内容

NSMutableData *content;