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Parse json with NSJSONSerialization class using objectForKey in iOS

I am new to iOS development. I use this code to connect to my REST web service and receive data in Json format.

    NSString *url=@"URL_Address";

    NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];

    NSURLResponse *resp = nil;
    NSError *err = nil;

    NSData *response = [NSURLConnection sendSynchronousRequest: theRequest returningResponse: &resp error: &err];

//    NSString * theString = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding]; 
//    NSLog(@"response: %@", theString);

    NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: response options: NSJSONReadingMutableContainers error: &err];

    if (!jsonArray) {
        NSLog(@"Error parsing JSON: %@", err);
    } else {
        for(NSDictionary *item in jsonArray) {
            NSLog(@" %@", item);
            NSLog(@"---------------------------------");
        }
    }

Now I want to separate them through objectForKey. I used this code inside the loop:

NSString *name = [item objectForKey:@"name"];

This does not work. I got this error:

2012-07-31 12:48:38.426 LearningAFNetworking[390:f803] -[__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x6844460
2012-07-31 12:48:38.428 LearningAFNetworking[390:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x6844460'
*** First throw call stack:
(0x13c8022 0x1559cd6 0x13c9cbd 0x132eed0 0x132ecb2 0x2f40 0x2bf8 0xd9a1e 0x38401 0x38670 0x38836 0x3f72a 0x290b 0x10386 0x11274 0x20183 0x20c38 0x14634 0x12b2ef5 0x139c195 0x1300ff2 0x12ff8da 0x12fed84 0x12fec9b 0x10c65 0x12626 0x254d 0x24b5 0x1)
terminate called throwing an exception(lldb)

Could you help me?

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5 answers

You need to access the 0array element item:

NSArray *mainArray = [item objectAtIndex:0];
(NSDictionary *obj in mainArray) {
     NSString *name = [obj objectForKey:@"name"];
}

When you received this error: -[__NSArrayM objectForKey:]you need to understand that the object you are trying to access is not a dictionary. This is an array ( __NSArrayM), so you need to access index 0 first and then start exploring the dictionary.

, .

+2

, , NSDictionary, NSArray, . valueForKeyPath, . , for :

NSArray *items = [jsonArray objectAtIndex:0];

for (NSDictionary *item in items){
    NSString *name = [item valueForKey:@"name"];
    // You can also get nested properties like this
    NSString *projectName = [item valueForKeyPath:@"project.name"]; 
}

, , "name", , valueForKey items, valueForKey . :

NSArray *items = [jsonArray objectAtIndex:0];
NSArray *names = [items valueForkey:@"name"];
+2

, objectForKey NSArray. NSString *name = [item objectForKey:@"name"]; NSString *name = [[item objectAtIndex: 0]objectForKey:@"name"];

0

NSArray

[[jsonArray objectAtIndex:0]objectForKey:@"object-key"];
0
-(void)clientServerCommunication
{
    NSURL *url = [NSURL URLWithString:@"http://182.72.122.106/iphonetest/getTheData.php"];
    NSURLRequest *req = [NSURLRequest requestWithURL:url];
    NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:req delegate:self];
    if (connection)
    {
        webData = [[NSMutableData alloc]init];
    }
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webData setLength:0];
}

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

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSDictionary *responseDict = [NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];

    /*Third party API
     NSString *respStr = [[NSString alloc]initWithData:webData encoding:NSUTF8StringEncoding];
     SBJsonParser *objSBJson = [[SBJsonParser alloc]init];
     NSDictionary *responseDict = [objSBJson objectWithString:respStr]; */
    resultArray = [[NSArray alloc]initWithArray:[responseDict valueForKey:@"result"]];
    NSLog(@"resultArray: %@",resultArray);
    [self.tableView reloadData];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    custcell=[tableView dequeueReusableCellWithIdentifier:CellIdentifier];



    if(custcell==nil)
    {

        custcell=[[[NSBundle mainBundle]loadNibNamed:@"custumCell" owner:self options:nil]objectAtIndex:0];

    }


    custcell.persnName.text=[[arr objectAtIndex:indexPath.row]valueForKey:@"Name"];
    //else if (objsegment.selectedSegmentIndex==1)
    //{
    custcell.persnAge.text=[[arr objectAtIndex:indexPath.row]valueForKey:@"Age"];

    [sortcontrol addTarget:self action:@selector(SegmentbtnCLK:) forControlEvents:UIControlEventValueChanged];

    //objsegment.selectedSegmentIndex=0;
    // }

    return custcell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Navigation logic may go here, for example:
     //Create the next view controller.
    detailViewController *detailViewController1 = [[detailViewController alloc]initWithNibName:@"detailViewController" bundle:nil];

 //detailViewController *detailViewController = [[detailViewController alloc] initWithNibName:@"detailViewController" bundle:nil];

 // Pass the selected object to the new view controller.

 // Push the view controller.
 detailViewController1.nextDict = [[NSDictionary alloc]initWithDictionary:[resultArray objectAtIndex:indexPath.row]];
 [self.navigationController pushViewController:detailViewController1 animated:YES];

    // Pass the selected object to the new view controller.

    // Push the view controller.
  //  [self.navigationController pushViewController:detailViewController animated:YES];
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    empName.text=[nextDict valueForKey:@"name"];
    deptlbl.text=[nextDict valueForKey:@"department"];
    designationLbl.text=[nextDict valueForKey:@"designation"];
    idLbl.text=[nextDict valueForKey:@"id"];
    salaryLbl.text=[nextDict valueForKey:@"salary"];
    NSString *ImageURL = [nextDict valueForKey:@"image"];
    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:ImageURL]];
    image.image = [UIImage imageWithData:imageData];
}
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