Objective-C JSON types

Question

I'm using NSJSONSerialization JSONObjectWithData:options:error: in an iOS 5 project to read a JSON string and convert it to a Foundation object. Is there an easy way to find out if the object or some of its children are arrays, dictionaries, numbers or strings?

Answer 1

You can check to see if the returned object is a certain class with the -isKindOfClass: method. For example, to check if it's an array:

id jsonObj = [NSJSONSerialization JSONObjectWithData:...]
if ([jsonObj isKindOfClass:[NSArray class]] {
    // Do array stuff...
}

Similarly for the other foundation types.

Answer 2

Please be careful about using NSJSONSerialization since it is only supported on iOS 5.0+ and Mac OS X 10.7+.

I think you can also have a try with third-party libraries, such as:

• JSONKit (faster than NSJSONSerialization per its introduction)
• SBJson

Both are easy to use and flexible.

Answer 3

All objects can answer their class. Even more useful, you can ask if something is a member of a class or any of it's subclasses:

id jsonParse;

if ([jsonParse isKindOfClass:[NSArray self]]) {
    for (id element in (NSArray *)jsonParse) {

        // and so on
    }
}