Re: Mutable Convenience Methods

FROM : Ben Lachman
DATE : Wed Feb 20 21:29:17 2008

On Feb 20, 2008, at 11:56 AM, j o a r wrote:

> On Feb 20, 2008, at 5:20 PM, Jonathon Mah wrote:
>

>> I think mutable subclasses should override the convenience methods 
>> of their superclass to return a mutable version. For example, 
>> [NSMutableArray array] and [NSMutableString string] both return 
>> mutable versions, but [NSMutableParagraphStyle 
>> defaultParagraphStyle] does not. Is this considered a bug in 
>> NSMutableParagraphStyle?

>
>
> The big difference between the API:s that you quote above is that 
> NSMutableArray and NSMutableString returns new instances, while 
> NSParagraphStyle returns a singleton, shared, instance. For this 
> reason, I don't think that this could be considered a bug, or that 
> it would make sense to have a similar method in 
> NSMutableParagraphStyle.


While I agree that this isn't a bug, I do think it would be worth 
while to have a mutable version or replacement convenience method. 
In general there are a few places where cocoa is really lacking in 
convenience methods and this is one of them*.  I call 
[[[NSParagraphStyle defaultParagraphStyle] mutableCopy] autorelease] 
so often that I have mutableDefaultParagraphStyle defined in one of 
my default categories.  It just trips one up to have 
NSMutableParagraphStyle return a NSParagraphStyle.  I doubt (m)any 
people rely on it being the actual singleton object that is returned, 
particularly if they're calling it from NSMutableParagraphStyle 
instead of just NSParagraphStyle.

->Ben

*others being creation of sort descriptors, attributed string and 
predicates

--
Ben Lachman
Acacia Tree Software

http://acaciatreesoftware.com

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