ios - 返回空的 NSURLConnection 数据

Question

我无法弄清楚为什么我的代码无法正常工作。我认为我做的一切都正确，php 脚本编码并显示它应该如何。有人可以查看我的代码并提出我做错了什么吗？

PHP:

$link = ...succesfully connects
if ($link){
    if (isset($_REQUEST['past'])) {
        $result = mysqli_query($link, 'SELECT * FROM messages WHERE id > '.
            mysqli_real_escape_string($link, $_REQUEST['past']).
            ' ORDER BY added LIMIT 50');
        $messages = array();
        echo json_encode($messages);
    } else {
        $result = mysqli_query($link, 'SELECT * FROM messages ORDER BY timeadded LIMIT 50');
        $messages = array();
        while ($row = mysqli_fetch_assoc($result)) {
            $messages[] = $row;
        }
        echo json_encode($messages);
    }
}

输出是这样的:

[{"id":"1","user":"me","message":"my first message","timeadded":"2014-02-11 12:47:55"},{"id":"2","user":"me","message":"my second message","timeadded":"2014-02-18 14:29:23"}]

这是我的 ViewController 代码:

h:
{
NSMutableData *responseData;
}
@property (nonatomic, strong) NSMutableArray *receivedData;


m:
@synthesize receivedData;

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[responseData setLength:0];
NSLog(@"received response");
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[responseData appendData:data];
NSLog(@"%@", receivedData);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(@"Succeeded! Received %d bytes of data",[responseData length]);
receivedData = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:nil];
NSLog(@"%@", responseData);
}

- (void)viewDidLoad
{
[super viewDidLoad];
[self getNewMessages];
}

- (void)getNewMessages {
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"messages.php?past=%d", lastId] relativeToURL:[NSURL URLWithString:@"http://www.mydomain.com/"]];

responseData = [NSMutableData dataWithCapacity:0];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:url];
[request setHTTPMethod:@"GET"];

 NSURLConnection *conn=[[NSURLConnection alloc] initWithRequest:request delegate:self];
 if (conn)
 {
     receivedData = [[NSMutableArray alloc]init];
     NSLog(@"sent request to server");
 }
}

我只是想在数组被反序列化后记录它，但它在日志中是空的。显示前两个日志，然后仅显示 ()。我在这里做错了什么？该应用程序构建和运行都很好，没有错误...提前致谢!

如果我添加一个 NSMutableData 变量并尝试像文档中那样进行操作，我在 didReceiveData 函数中获得的数据如下所示:<5b5d>。这是什么意思？

这是我收到的回复:

{ status code: 200, headers {
Connection = "Keep-Alive";
"Content-Type" = "text/html";
Date = "Wed, 19 Feb 2014 00:03:30 GMT";
"Keep-Alive" = "timeout=10, max=30";
Server = Apache;
"Transfer-Encoding" = Identity;
Vary = "Accept-Encoding";
} }

回答:显然 PHP 脚本是错误的...它不喜欢 isset。一旦我摆脱了它，我就会返回我的数据。按照 iOS 文档，一切正常。

Answer 1

您没有正确使用 connection:didReceiveData:。您应该创建一个 NSMutableData 实例，并将在 connection:didReceiveData: 中收到的数据附加到它。您应该在 connectionDidFinishLoading: 中对您的数组进行转换:您尚未实现。查看 Apple 在“URL 加载系统编程指南”中显示的代码作为示例。