Question

so I’m having the most difficult of time pulling values out of an NSDictionary. Right now I just have a dictionary that is populated from a JSON call and it only contains a key named ‘Success’ with a value of 0 or 1.

How do I do a conditional on that value to check if its 0 or 1? I’ve tried a bunch of things, but I’m not getting anywhere. Here’s my current code:

[[jsonDictionary objectForKey:@"Success"] isEqualToNumber:1]

I’m getting passing argument 1 of 'isEqualToNumber:' makes pointer from integer without a cast' as a warning, and the app crashes when it hits that line anyway.

And a subquestion, what’s the difference between objectForKey and valueForKey? Which one should I use by default?

Anyway, this noob in Objective-C would truly appreciate some help on this. Thanks in advance!

Answer 1

Since dictionaries contain Objective-C objects, an entry containing a number is an NSNumber instance. NSNumber provides a convenience method, -intValue, for extracting its underlying int value:

if ([[jsonDictionary objectForKey:@"Success"] intValue] == 1) { … }

Note that NSNumber has other convenience methods for extracting its underlying value as other C data types.

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In most cases, you should use -objectForKey: instead of -valueForKey:. The former is the canonical method to obtain an entry in the dictionary and is declared in NSDictionary. The latter is declared in NSObject and is used in Key-Value Coding contexts, where the key must be a valid KVC key, and there’s additional processing — for instance, if you’re using -valueForKey: in a dictionary with a key that starts with @, that character is stripped from the key and [super valueForKey:key] is called.