How to get values from a dictionary in iOS

Question

I am new to iOS. I created a login page and everything works fine. I used JSON for checking username and password and got the response from server in a dictionary format. I want to extract the values from the dictionary and check them in my program. The response which I get from the server is:

json: {
        error = 0;
        msg = "";
        value = {
                  user = false;
                };
      };

First I want to check if the value with the key error is 0 or 1. Then I want to check the value with the key user. I don't know how I should code to check it. Can anyone help?

The code which I tried is below:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *respString = [[NSString alloc] initWithData:loginJSONData encoding:NSUTF8StringEncoding];

    SBJsonParser *objSBJSONParser = [[SBJsonParser alloc] init];

    NSDictionary *json = [[NSDictionary alloc] initWithDictionary:[objSBJsonParser objectWithString:respString]];

    NSLog(@"json: %@",json);

    NSString *error = [json objectForKey:@"error"];

    NSLog(@"error: %@", error);

    if ([error isEqualToString:@"o"])
    {
        NSLog(@"login successful");
    }
    else
    {
        NSLog(@"login fail");
    }
}

Answer 1

Using modern Objective-C, accessing things in arrays and dictionaries become easier.

You should use the following syntax:

id<NSObject> value = dictionary[@"key"];

Similarly,

id<NSObject> value = array[1]; // 1 is the index

Applying the above to the question:

NSString *error = json[@"error"];

NSDictionary *value = json[@"value"];

BOOL user = [json[@"value"][@"user"] boolValue];

As in the above line, nesting is allowed, but it is not a good practice.

Answer 2

NSNumber *error = [json objectForKey:@"error"];
if ([error intValue] == 0)
{
    NSLog(@"login successful");

    NSDictionary *value = [json objectForKey:@"value"];
    NSNumber *user = [value objectForKey:@"user"];
    if ([user boolValue])
    {
        NSLog(@"user == true");
    }
    else
    {
        NSLog(@"user == false");
    }
}
else
{
    NSLog(@"login failed");
}