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macOS NSConcreteAttributedString mutableString crash

M

mdeh

macrumors 6502
Original poster
Jan 3, 2009
345
2
Hi all,
I have a problem that I cannot understand! :confused:

According to the documentation, there is a method "mutableString" which, in the NSMutableAttributedString class
Returns the character contents of the receiver as an NSMutableString object.
Click to expand...

So, with this code

Code: 
NSMutableString * s = [_mString mutableString];

I would have expected s to be a mutableString. Here is the error:

-[NSConcreteAttributedString mutableString]: unrecognized selector sent to instance 0x100474560
Click to expand...

Changing to this code:

Code: 
NSString * s = [_mString string];

eliminates this issue...but the question is why? The literature that I have looked at does not seem to have an answer.

Thanks as usual.
 
K

kainjow

Moderator emeritus
Jun 15, 2000
7,958
7
NSMutableAttributedString's methods aren't inherited by NSAttributedString. So any method specifically defined for NSMutableAttributedString will not work on NSAttributedString.

If you want a mutable string for NSAttributedString just call mutableCopy on the string.

How is _mString created?
 
M

mdeh

macrumors 6502
Original poster
Jan 3, 2009
345
2
kainjow said:
NSMutableAttributedString's methods aren't inherited by NSAttributedString. So any method specifically defined for NSMutableAttributedString will not work on NSAttributedString.
How is _mString created?
Click to expand...

Kainjow...thanks, first off.

-mString is created by by taking the textStorage property of an NSTextView, and setting an NSMutableAttributed string using an accessor thus.


Code: 
-(void) setMString:(NSMutableAttributedString *) m
{
	if ( m == nil)
	{
		return;
	}
	m = [m copy];
	[_mString release];
	_mString = m;

Earlier, I removed the actual use of the setter to make it read more easily, but here is the actual call to set it.

Code: 
[[self cypherCenter] setMString:[[self cypherField]textStorage]];

Where cypherCenter is the class that has the accessor setMString.


Where I am a little confused is that the method:
- (NSMutableString *)mutableString is described within the NSMutableAttributedString Class and shows that an NSMutableString is returned, which is what I thought I was doing :), but apparently not! Well, it was causing this issue. Still a little confused, but thanks for your input.
 
K

kainjow

Moderator emeritus
Jun 15, 2000
7,958
7
Code: 
m = [m copy];

Try using mutableCopy here.

Have a read through the section Copying Mutable Versus Immutable Objects (at the bottom). Basically, if you call copy on a mutable object, it will return an immutable one instead. This applies to things like NSArray, NSString, NSDictionary, etc., and other classes that have a separate mutable version.
 
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