NSJSONSerialization unboxes NSNumber?

Question

I'm using NSJSONSerialization to turn a JSON document into the Core Foundation types.

I have a field in my JSON which is a "number". It's sometimes and integer, sometimes a float.

Now, the problem is when NSJSONSerialization turns my JSON into an NSDictionary and I try to extract the number using objectForKey, sometimes it's an int, and sometimes it's a double. It seems NSJSONSerialization doesn't simply leave it in an NSNumber wrapper, but actually unboxes the value, and inserts that into the NSDictionary.

Very strange. I thought you we're supposed to put primitives into an NSDictionary. So the problem I have now is that I don't know what type (int or double) I should be casting to to preserve the actual number value.

Anyone know a way out?

No, it can't do that as you can only store objects in a `NSDictionary` so it has to keep them boxed. — trojanfoe, Feb 19 '13 at 13:58
Strange, right? But that's exactly what's happening! I am using AFNetwroking (which uses NSJSONSerialization under the hood), if that makes a difference. — elsurudo, Feb 19 '13 at 14:03

score 3 · Accepted Answer · answered Feb 19 '13 at 14:13

You can get primitive type from NSNumber. Just use following code snippet:

    const char* type = [theValue objCType];
if (strcmp (type, @encode (NSInteger)) == 0) {
    //It is NSInteger
} else if (strcmp (type, @encode (NSUInteger)) == 0) {
    //It is NSInteger
} else if (strcmp (type, @encode (int)) == 0) {
    //It is NSUInteger
} else if (strcmp (type, @encode (float)) == 0) {
    //It is float
} else if (strcmp (type, @encode (double)) == 0) {
    //It is double
} else if (strcmp (type, @encode (long)) == 0) {
    //It is long
} else if (strcmp (type, @encode (long long)) == 0) {
    //It is long long
}

And etc.

Since this would have been a solution had my problem been a real problem, I'm going to mark this as correct. — elsurudo, Feb 19 '13 at 14:26

score 0 · Answer 2 · answered Feb 19 '13 at 14:16

Turns out they were NSNumbers all along, and I am just inexperienced at debugging. I was just confused and thought they were int and double values, because that is how the debugger presents them. So it's the debugger that was unboxing, not NSJSONSerialization...

NSJSONSerialization unboxes NSNumber?

2 Answers2

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