在另一位 SO 专家用户的帮助下,我正在实现一种方法将 viewController 连接到远程 PHP 文件以更新 MySQL 字段值并使其也更新一个UILabel
。
我从 PHP 文件中回显的 JSON 值是这样的格式:["34"]。
这是方法:
- (IBAction)votarAction:(id)sender {
//URL definition where php file is hosted
dispatch_queue_t backgroundQueue = dispatch_queue_create("com.mycompany.myqueue", 0);
dispatch_async(backgroundQueue, ^{
int categoriaID = [[detalleDescription objectForKey:@"idEmpresa"] intValue];
NSString *string = [NSString stringWithFormat:@"%d", categoriaID];
NSLog(@"ID EMPRESA %@",string);
NSMutableString *ms = [[NSMutableString alloc] initWithString:@"http://mujercanariasigloxxi.appgestion.eu/app_php_files/cambiarvaloracionempresa.php?id="];
[ms appendString:string];
// URL request
NSLog(@"URL = %@",ms);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:ms]];
//URL connection to the internet
NSData *responseData = [[NSURLConnection alloc]initWithRequest:request delegate:self];
NSLog(@"responseData= %@",responseData);
//Parse JSON
NSError *error = nil;
NSArray * json = [NSJSONSerialization
JSONObjectWithData:responseData
options: NSJSONReadingMutableContainers
error: &error];
int valoracionNumber = [[json objectAtIndex:0] integerValue];
dispatch_async(dispatch_get_main_queue(), ^{
//update your label
NSString *labelValue = [NSString stringWithFormat:@"%d", valoracionNumber];
self.valoracionLabel.text = labelValue;
});
});
}
这是引发的异常:
2014-02-28 22:45:16.921 Vive Gran Canaria[928:582b] responseData= <NSURLConnection: 0xf050bc0> { request: <NSURLRequest: 0x9de3d40> { URL: http://mujercanariasigloxxi.appgestion.eu/app_php_files/cambiarvaloracionempresa.php?id=25 } }
2014-02-28 22:45:16.922 Vive Gran Canaria[928:582b] -[NSURLConnection bytes]: unrecognized selector sent to instance 0xf050bc0
2014-02-28 22:45:16.947 Vive Gran Canaria[928:582b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURLConnection bytes]: unrecognized selector sent to instance 0xf050bc0'
*** First throw call stack:
(
0 CoreFoundation 0x00fca5e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x02c5c8b6 objc_exception_throw + 44
2 CoreFoundation 0x01067903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x00fba90b ___forwarding___ + 1019
4 CoreFoundation 0x00fba4ee _CF_forwarding_prep_0 + 14
5 Foundation 0x029a308c -[_NSJSONReader findEncodingFromData:withBOMSkipLength:] + 36
6 Foundation 0x029a323b -[_NSJSONReader parseData:options:] + 63
7 Foundation 0x029a3800 +[NSJSONSerialization JSONObjectWithData:options:error:] + 161
8 Vive Gran Canaria 0x00009bca __44-[DetalleEmpresaViewController votarAction:]_block_invoke + 602
9 libdispatch.dylib 0x02f5b7f8 _dispatch_call_block_and_release + 15
10 libdispatch.dylib 0x02f704b0 _dispatch_client_callout + 14
11 libdispatch.dylib 0x02f5e07f _dispatch_queue_drain + 452
12 libdispatch.dylib 0x02f5de7a _dispatch_queue_invoke + 128
13 libdispatch.dylib 0x02f5ee1f _dispatch_root_queue_drain + 83
14 libdispatch.dylib 0x02f5f137 _dispatch_worker_thread2 + 39
15 libsystem_c.dylib 0x03288e72 _pthread_wqthread + 441
16 libsystem_c.dylib 0x03270daa start_wqthread + 30
)
libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)
这是PHP文件中回显JSON数组的部分:
$arr = array();
$rs = mysql_query("SELECT * FROM tbempresas where idEmpresa='$id'");
while ($obj = mysql_fetch_assoc($rs)) {
$arr[] = $obj['valoracionEmpresa'];
}
echo json_encode($arr);
创建一个NSURLConnection
的对象而不是NSData
作为响应,你将在NSURLConnection
的委托方法中获取数据。
NSURLConnection *connection=[[NSURLConnection alloc]initWithRequest:request delegate:self];
#pragma NSURLConnection Delegate Methods
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
//buffer is the object Of NSMutableData and it is global,so declare it in .h file
buffer = [NSMutableData data];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[buffer appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//Here You will get the whole data
NSArray *array = [NSJSONSerialization JSONObjectWithData:buffer options:0 error:&jsonParsingError];
//And you can used this array
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
//if any error occurs..
}
这段代码有很多错误。 让我们从这一行开始:
NSData *responseData = [[NSURLConnection alloc]initWithRequest:request delegate:self];
这将返回NSURLConnection
的实例,但您将其分配给NSData
变量。 这意味着对NSURLConnection
如何运作的根本误解。 由于您使用的是initWithRequest:delegate:
因此连接将以异步方式处理,这意味着您将无法在 votarAction:
中更新标签。
您需要从 NSURLConnectionDataDelegate
协议中实现一些方法来读取数据。 检测到连接已关闭后,您可以处理数据并将其写入标签。
至少你需要实现:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
获取响应数据。 您确实应该实现其他委托方法来处理响应状态、失败等...... 或者,只是使用AFNetworking
,直到以后再忘记大部分细节。