CODEWITHSUNDEEP
objective-ccastingnsmutablestring
user141302
user141302

Reputation:

How to initialize NSString to NSMutableString?

Is there any way to initialize NSString to NSMutableString? and also reverse order?

-(void)st:(NSString *)st
{
  NSMutableString str = st; // gives warning..
  NSLog(@"string: %@", str);
}

Upvotes: 7

Views: 8221

Answers (4)

Joe Cannatti
Joe Cannatti

Reputation: 5079

You can set an NSMutableString to an NSString, but not the other way around

NSString *str =  [NSMutableString alloc]init];

is okay, but 

NSMutableString *str = [[NSString alloc]init];

is not. This is because an NSMutableString is a subclass of NSString, so it 'is a' NSString. You can however create a mutable string from an NSString with 

NSMutableString *mStr = [str mutableCopy];

Upvotes: 4

Dan Beaulieu
Dan Beaulieu

Reputation: 19954

Swift 2.0

For Swift users, the following works in Xcode 7.

var str : String = "Regular string"
var mutableStr : NSMutableString = NSMutableString(string: str)

Upvotes: 1

notnoop
notnoop

Reputation: 59299

NSString is an immutable representation (or a readonly view at worst). So you would need to either cast to a NSMutableString if you know it's mutable or make a mutable copy:

-(void)st:(NSString *)st
{
  NSMutableString *str =  [[st mutableCopy] autorelease];
  NSLog(@"string: %@", str);
}

I autoreleased it because mutableCopy returns a newly initialized copy with a retain count of 1.

Upvotes: 11

Bryan Henry
Bryan Henry

Reputation: 8408

NSString *someImmutableString = @"something";
NSMutableString *mutableString = [someImmutableString mutableCopy];

Important! mutableCopy returns an object that you own, so you must either release or autorelease it.

Upvotes: 4

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