exception __NSarrayM objectforkey unrecognized selector sent to instance [closed] - iphone

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i'm trying to make login page that get data fro php file by Json. it works fine until i use this sentence [jsonData objectForKey:#"state"] , an exception appears.
i tried to make another dictonary like some answers to question before. but nothing is working with me.
Output :
Response code : 200
Resonse ==> [{"state":"true"}]
JasonData ({state = true})
Then the exception
-[__NSarrayM objectforkey:]: unrecognized selector sent to instance
i'm new to objctive-C
if you could help me.
i will be greatfull
- (IBAction)loginClicked:(id)sender
{
#try
{
if([[txtUserName text] isEqualToString:#""] || [[txtPassword text] isEqualToString:#""] ) {
[self alertStatus:#"Please enter both Username and Password" :#"Login Failed!"];
} else {
NSString *post =[[NSString alloc] initWithFormat:#"username=%#&password=%#",[txtUserName text],[txtPassword text]];
NSLog(#"PostData: %#",post);
NSURL *url = [NSURL URLWithString:#"http://localhost/services/pages/login.php"];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:#"%d", [postData length]];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:url];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
NSError *error = [[NSError alloc] init];
NSHTTPURLResponse *response = nil;
NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSLog(#"Response code: %d", [response statusCode]);
if ([response statusCode] >=200 && [response statusCode] <300)
{
NSString *responseData = [[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
NSLog(#"Response ==> %#", responseData);
SBJsonParser *jsonParser = [SBJsonParser new];
NSDictionary *jsonData = (NSDictionary *) [jsonParser objectWithString:responseData error:nil];
NSLog(#"%#",jsonData);
NSLog(#"%#",[jsonData objectForKey:#"state"]);
NSString *state = [(NSString*) [jsonData objectForKey:#"state"] lowercaseString ];
NSLog(#"%#", state);
if([state isEqualToString:#"true"])
{
NSLog(#"Login SUCCESS");
[self alertStatus:#"Logged in Successfully." :#"Login Success!"];
}
else
{
NSString *error_msg = (NSString *) [jsonData objectForKey:#"error_message"];
[self alertStatus:error_msg :#"Login Failed!"];
}
}
else
{
if (error) NSLog(#"Error: %#", error);
[self alertStatus:#"Connection Failed" :#"Login Failed!"];
}
}
}
#catch (NSException * e)
{
NSLog(#"Exception: %#", e);
[self alertStatus:#"Login Failed." :#"Login Failed!"];
}

Answer 1

The JSON data returned by the webserive seems to be an NSArray and not NSDictionary. You can check that here,
id jsonData = [jsonParser objectWithString:responseData error:nil];
if([jsonData isKindOfClass:[NSDictionary class]]) {
NSLog(#"Dictionary");
}
else if([jsonData isKindOfClass:[NSArray class]]) {
NSLog(#"Array");
}
Your code crashes because you are assuming the parsed response as NSDictionary and passing the objectForKey: method. Being an NSArray it cannot recognise this method and raises an exception.
Now if it is an NSArray with one dictionary inside, you can read it as below,
[[jsonData objectAtIndex:0] objectForKey:#"state"];
Hope that helps!