NSMutable Dictionary adding objects

Question

Is there a more efficient way to add objects to an NSMutable Dictionary than simple iteration?

Example:

// Create the dictionary

NSMutableDictionary *myMutableDictionary = [NSMutableDictionary dictionary];    

// Add the entries

[myMutableDictionary setObject:@"Stack Overflow" forKey:@"http://stackoverflow.com"];
[myMutableDictionary setObject:@"SlashDotOrg" forKey:@"http://www.slashdot.org"];
[myMutableDictionary setObject:@"Oracle" forKey:@"http://www.oracle.com"];

Just curious, I'm sure that this is the way it has to be done.

Andrew Johnson · Accepted Answer · 2009-07-12 22:59:23Z

20

NSDictionary *entry = [NSDictionary dictionaryWithObjectsAndKeys:
  [NSNumber numberWithDouble:acceleration.x], @"x",
  [NSNumber numberWithDouble:acceleration.y], @"y",
  [NSNumber numberWithDouble:acceleration.z], @"z",
  [NSDate date], @"date", 
  nil];

answered Jul 12, 2009 at 22:59

Andrew Johnson

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stefanB · Accepted Answer · 2009-07-12 23:17:22Z

15

If you have all the objects and keys beforehand you can initialize it using NSDictionary's:

dictionaryWithObjects:forKeys:

Of course this will give you immutable dictionary not mutable. It depends on your usage which one you need, you can get a mutable copy from NSDictionary but it seems easier just to use your original code in that case:

NSDictionary * dic = [NSDictionary dictionaryWith....];
NSMutableDictionary * md = [dic mutableCopy];
... use md ...
[md release];

edited Jul 12, 2009 at 23:17

answered Jul 12, 2009 at 22:57

stefanB

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2 Comments

djt9000 Over a year ago

Thank you for the second opinion. I just wanted to be sure I was not missing anything and to see if there was something a bit more efficient / elegant.

stefanB Over a year ago

I was as well searching for an option to initialize NSMutableDictionary with objects and keys like you can do for NSDictionary but I can't find anything ...

Community · Accepted Answer · 2017-05-23 12:25:08Z

8

Allow me to add some information to people that are starting.

It is possible to create a NSDictionary with a more friendly syntax with objective-c literals:

NSDictionary *dict = @{ 
    key1 : object1, 
    key2 : object2, 
    key3 : object3 };

edited May 23, 2017 at 12:25

CommunityBot

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answered Jul 8, 2013 at 13:12

Tiago Almeida

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2 Comments

vvMINOvv Over a year ago

should you end the list with a nil?

Tiago Almeida Over a year ago

@vvMINOvv No need :). The same with NSArrays literals :)

HiDeoo · Accepted Answer · 2016-07-22 06:52:20Z

0

NSMutableDictionary *example = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@5,@"burgers",@3, @"milkShakes",nil];

The objects come before the keys.

edited Jul 22, 2016 at 6:52

HiDeoo

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answered Jul 22, 2016 at 2:51

Jeremiah Radich

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