How to check if JSON object contains values

Question

I have a JSON array that I parse. I parse the values from the key Staff, however sometimes the Staff object contain no values;

Expected return;

enter image description here

But sometimes it returns:

enter image description here

Which causes the app to crash because key[@"staff"][@"staff_id"] doesnt exist.

Ive tried:

if (key[@"staff"][@"staff_id"]){
     //Parse staff 
}
else{

    //staff is empty

}

But this crashes as well because I think it still looks for the [@"staff_id"] which doesnt exist.

I've also tried

if (![key[@"staff"][@"staff_id"] isKindOfClass:[NSNull class]])

And

if (![key[@"staff"] isKindOfClass:[NSNull class]])

Any help is greatly appreciated. :)

l0gg3r · Accepted Answer · 2014-12-05 15:27:16Z

2

That's a great example of shitty backend.
On the first example enter image description here staff is a Dictionary, on the second example is an Array.

You need to ask your backend developer, to decide and always return either Array, or Dictionary.

BTW, you can workaround it

if ([key[@"staff"] isKindOfClass:[NSDictionary class]] && key[@"staff"][@"staff_id"]) {
    id staffId = key[@"staff"][@"staff_id"];
} else {
    // Staff is empty
}

answered Dec 5, 2014 at 15:27

l0gg3r

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3 Comments

Miknash Over a year ago

I would add to the if condition && [key objectForKey:@"staff_id"] just in case since returned JSON seems unconsistent

l0gg3r Over a year ago

@NickCatib fixed, DevC that's great :) , if it fixed the problem, please mark it correct for further readers.

DevC Over a year ago

@l0gg3r had to wait a few mins before I could accept according to SO, but all working thank you :)

gnasher729 · Accepted Answer · 2014-12-05 16:16:50Z

You will only get object of class NSNull if the JSON contained a null value. For example a dictionary { "key": null } will contain a key/value pair with a key "key" and a value [NSNull null]. Instead of using "isKindOfClass" you can compare with [NSNull null], because there is only ever one NSNull object. If your JSON doesn't contain null values, that won't happen.

If your JSON sometimes contains a dictionary, and sometimes an array, well that's tough. Blame the guys creating the JSON. You can write for example:

id keyObject = ...; 
NSDictionary* keyDictionary = keyObject; 
NSArray* keyArray = keyArray; 

if ([keyDictionary isKindOfClass:[NSDictionary class]]) {
    .. you've got a dictionary
} else if ([keyArray isKindOfClass [NSArray class]]) { 
    .. you've got an array 
} else if (keyObject == nil) {
    .. there wasn't actually any key object
} else if (keyObject == [NSNull null]) { 
    .. your JSON contained "key": null
} else {
    .. your JSON contained a string, number, or boolean value
}

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