Checking if JSON key is present - objective-c

Question

Here's the scenario; I have a JSON response from a API. I obtain a response from the API as follows:
[request setURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://apitest.maranatha.org/api/SiteGroupStagings?countryId=%i",[country getCountryID]]]];
[request setHTTPMethod:#"GET"];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[request setValue:token forHTTPHeaderField:#"Token"];
NSData *returnData = [NSURLConnection sendSynchronousRequest: request returningResponse: nil error: nil];
if (returnData) {
NSDictionary* jsonResponse = [NSJSONSerialization
JSONObjectWithData:returnData options:NSJSONReadingMutableContainers
error:&error];
}
The API will return a JSON array of objects when the API call is correct, the return looks like this:
[
{},
{},
...
]
If there is any problem processing the request on the server side (other than lack of internet connectivity on the client side), the response from the API is a as follows:
{
"message": "In lorem ipsum"
}
I want to check if that key/value pair is present, to be able to alert the user, and not attempt to process the response which would cause an exception to occur.
I've tried the following approach, but it doesn't seem to work, it seems it can always find a message key, even when the JSON response is an array of objects.
if ([jsonResponse valueForKey:#"message"]) {
NSLog(#"%#", [jsonResponse valueForKey:#"message"]);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error"
message:[jsonResponse valueForKey:#"message"]
delegate:self
cancelButtonTitle:#"Ok" otherButtonTitles:nil];
[alert show];
}
else {
//consume the JSON response
}
How can I successfully check if the response from the API contains the message key/value pair?

Answer 1

It sounds like your server API returns JSON entities with a key "message" for successful requests as well, correct? If that's the case, maybe try this:
if (jsonResponse[#"message"] &&
[jsonResponse[#"message"] isKindOfClass:[NSString class]] &&
[jsonResponse[#"message"] isEqualToString:#"In lorem ipsum"])
{
// Alert
}
This should give you better (but not necessarily complete) protection against runtime variance in the content of the JSON entity as a whole.

Answer 2

Thanks to #fullofsquirrels I got an idea of how to solve the problem.
If a JSON is an JSON Array, [NSJSONSerialization] will make it a NSArray, so the easiest way was to check if my response was an array, or if it wasn't. Here's my solution.
if (![jsonResponse isKindOfClass:[NSArray class]]) {
NSLog(#"%#", [jsonResponse valueForKey:#"message"]);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error"
message:[jsonResponse valueForKey:#"message"]
delegate:self
cancelButtonTitle:#"Ok" otherButtonTitles:nil];
[alert show];
}
else {
//consume API
}