CODEWITHSUNDEEP
objective-cnsdictionarystrong-references
notadam
notadam

Reputation: 2884

Does NSMutableDictionary keep a strong reference to an object I put in it via 'setValue:forKey:'?

According to Apple's documentation, if I add an object to an NSMutableDictionary via the setObject:forKey: method, the dictionary will keep a strong reference to it.

But what about the setValue:forKey: method? The documentation doesn't say anything about the kind of reference to the object added via this method. Is it the same as the other one? Does the dictionary keep a strong reference to the object added via this method as well?

Upvotes: 1

Views: 1653

Answers (2)

rmaddy
rmaddy

Reputation: 318854

NSMutableDictionary (and NSMutableArray) keeps strong references to any object added to it, no matter how it is added.

Upvotes: 4

wjl
wjl

Reputation: 7361

NSMutableArray and NSArray keep strong references to objects they contain. These objects are either added using the literal constructor @[myObject, myObject2, ...], the initializers of NSArray, or the add/insert methods of NSMutableArray.

If you're looking for key/value storage like a map, you want to use NSDictionary/NSMutableDictionary instead. The setValue:forKey: method you're talking about is for key-value coding compliance, which is different.

Additionally, NSDictionary and NSMutableDictionary keep strong references to value objects, and keep copy references to keys (which must comply to the NSCopying protocol).

Upvotes: 3

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