How to know if a JSONObject contains a key?

el_pablo

Hey guys,

I'm trying to figure out how to know if a JSONObject contains a key. I tried the method myJSON.containsKey("theKey"), but Processing gives me the error "The function containsKey(String) does not exist".

I've also tried "myJSON.has ("theKey")" and it does not work either.

It's getting me crazy!!

Thanks for any help!

koogs

What type is myJSON?

blindfish

Maybe you need to use parseJSONObject first?

Chrisir

well, each json interface is different (depending if its about weather, movies or animals... e.g.)

each json interface holds different keys

so either

• you have the documentation of the specification of that json interface

• or you use println to just print out the whole json string. Then you can look up the keys you need. And the structure, often there are json-arrays or other json-objects embedded

when you ask for a key that doesn't exist the var should be null. So you can write your own check function

boolean containsKey(JSONObject jsonObj, String key) {

    if (jsonObj==null) 
        println("jsonObj was null"); 
        return false; 
    }    
    if (key==null) 
        return false; 

    if (key.equals("")) 
        return false; 

    String name = null;

    name = jsonObj.getString(key);

    if (name==null) 
        return false; 
     else 
        return true; 


}

blindfish

@Chrisir: we first need to establish where the json is coming from and if it has been parsed into a json object...

el_pablo

Thanks for answering. The error was my bad...

I provide the JSON from a client sketch.