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How to check if an NSDictionary or NSMutableDictionary contains a key?

Answer 1

+5 A:

objectForKey will return nil if a key doesn't exists.

Adirael 2010-05-06 21:30:04

And what if the key does exist, but it's corresponding value is nil?

Fyodor Soikin 2010-05-06 21:30:32

That's not possible. You can't add nil to a NSDictionary. You would have to use `[NSNull null]` instead.

Ole Begemann 2010-05-06 21:39:17

@fyodor an nsdictionay will throw an NSInvalidArgumentException if you attempt to insert a nil value, so there should never be a case where a key exists, but the corresponding value is nil.

Brad Smith 2010-05-06 22:50:17

Answer 2

+2 A:

if ([mydict objectForKey:@"mykey"]) {
    // key exists.
}
else
{
    // ...
}

ChristopheD 2010-05-06 21:30:27

Answer 3

+2 A:

if ([[dictionary allKeys] containsObject:key) {
    // contains key
}

or

if ([dictionary objectForKey:key]) {
    // contains key
}

Aleksejs 2010-05-06 21:31:43

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How to check if an NSDictionary or NSMutableDictionary contains a key?

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