CODEWITHSUNDEEP
iosobjective-cnsmutabledictionary
Sibir
Sibir

Reputation: 313

Initialize NSMutableDictionary

I am developing an iOS application in which I want to use an NSMutableDictionary. Basically what I am doing is converting java code to objectiveC.

So in java I have something like this:

Map<String, ClassA> dict1 = new HashMap<>();
Map<Integer,Character> dict2 = new HashMap<>();
Map<Integer, Map<String,String>> dict3 = new HashMap<>();

Can someone please guide me as what would be the Obj-C equivalent code for the above three lines using NSMutableDictionary and also how can I set and get the pairs in/from the dictionaries.

Upvotes: 3

Views: 23353

Answers (2)

jervine10
jervine10

Reputation: 3077

Since Objective C does not have generic types all you have to type is this:

NSMutableDictionary *dict1 = [[NSMutableDictionary alloc] init];
NSMutableDictionary *dict2 = [[NSMutableDictionary alloc] init];
NSMutableDictionary *dict3 = [[NSMutableDictionary alloc] init];

There's a couple ways to get and set values. The shorthand form is much like accessing arrays. To set a value with shorthand:

dict1[@"key"] = @"value";

To get a value with shorthand:

NSString *value = dict1[@"key"];

More verbose syntax is like so:

[dict1 setObject:@"value" forKey:@"key"];
NSString *value = [dict1 valueForKey:@"key"];

Upvotes: 11

trojanfoe
trojanfoe

Reputation: 122391

The Objective-C collection classes are not strongly typed so all three dictionaries would be created using:

NSMutableDictionary *dictX = [NSMutableDictionary new];

In order to populate the dictionary use [NSMutableDictionary setObject:forKey:]:

[dict1 setObject:classAInstance
          forKey:@"key1"];
[dict2 setObject:[NSString stringWithFormat:@"%c", character]
          forKey:@(1)];
[dict3 setObject:@{ @"innerKey" : @"innerValue" }
          forKey:@(2)];

etc.

Upvotes: 12

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