CODEWITHSUNDEEP
iphoneobjective-cnsdictionary
user773578
user773578

Reputation: 1161

Using NSDictionaries

I have a number of NSString objects I want to save into an NSDictionary.

How is an NSDictionary initialized with the keys and do the values need to be set there and then or can the dictionary be setup using just the keys and the objects later set?

Upvotes: 0

Views: 467

Answers (2)

Abizern
Abizern

Reputation: 150605

To start with here's a link to the NSDictionary documentation, and NSMutableDictionary

You can create a NSMutableDictionary with just keys by passing [NSNull null] as the object for that key. It's important to use a mutable dictionary here otherwise you won't be able to change the dictionary after you've created it, and a dictionary that just has keys instead of objects is of little use.

That is what NSNull is for: to provide null values for collection types that don't allow nils.

Upvotes: 3

marzapower
marzapower

Reputation: 5611

A dictionary can be initialized both as empty or as a list of (value,key) pairs.

Initializing the dictionary just with keys and not values is useless/meaningless in Objective-C, since it will be equivalent to a void initialization.

If you want to create a dictionary and want to be able to set objects later, you have to use a NSMutableDictionary, that has not a static initialization of its data, through its setObject:forKey: method.

Upvotes: 2

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