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Stephane
Stephane

Reputation: 5076

How do I use the writeToFile method on an NSMutableDictionary?

I would like to use a method (writeToFile) only available for NSDictionary to a NSMutableDictionary object. So, how do I convert this NSMutableDictionary object to NSDictionary?

Upvotes: 9

Views: 22351

Answers (6)

Daniel Galasko
Daniel Galasko

Reputation: 24267

To address the actual question title and not the contents (since I searched for this Q) you can actually rely on copyWithZone: to get down to an Immutable Dictionary.

NSMutableDictionary *mutableDict = [[NSMutableDictionary alloc] init];
mutableDict[@"key"] = @"value";
NSDictionary *immutableDict = [mutableDict copy];

Upvotes: 1

Yoga
Yoga

Reputation: 1196

For those coming here genuinely looking for conversion from NSMutableDictionary to NSDictionary :

NSMutableDictionary *mutableDict = [[[NSDictionary alloc] initWithObjectsAndKeys:
                              @"value", @"key"] mutableCopy];

NSDictionary *dict = [NSDictionary dictionaryWithDictionary:mutableDict]; //there you have it

Upvotes: 13

zaph
zaph

Reputation: 112873

A NSMutableDictionary is a NSDictionary since it is a subclass. Typically the relationship of a subclass to it's superclass is called: "is a".

Upvotes: 3

adpalumbo
adpalumbo

Reputation: 3031

As already discussed here:

How to save a NSMutableDictionary into a file in documents?

you don't need to convert it.

But if you really want to, just use the copy method on your NSMutableDictionary or the dictionaryWithDictionary: method on NSDictionary. Both provide an NSDictionary from an NSMutableDictionary.

Upvotes: 6

Jeremy Flores
Jeremy Flores

Reputation: 483

NSMutableDictionary is a subclass of NSDictionary, so the writeToFile method should be available for your object without having to do any casting or conversions.

Upvotes: 7

Daryl Teo
Daryl Teo

Reputation: 5495

NSMutableDictionary inherits from NSDictionary. So, writeToFile should be available to both classes.

Upvotes: 14

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