NSArray @property backed by a NSMutableArray

Question

I've defined a class where I'd like a public property to appear as though it is backed by an NSArray. That is simple enough, but in my case the actual backing ivar is an NSMutableArray:

@interface Foo {     NSMutableArray* array; } @property (nonatomic, retain) NSArray* array;  @end 

In my implementation file (*.m) I @synthesize the property but I immediately run into warnings because using self.words is the same as trying to modifying an NSArray.

What is the correct way to do this?

Thanks!

Answer 1

I would declare a readonly NSArray in your header and override the getter for that array to return a copy of a private NSMutableArray declared in your implementation. Consider the following.

Foo.h

@interface Foo  @property (nonatomic, retain, readonly) NSArray *array;  @end 

Foo.m

@interface Foo ()  @property (nonatomic, retain) NSMutableArray *mutableArray  @end  #pragma mark -  @implementation Foo  @synthesize mutableArray;  - (NSArray *)array {     return [[self.mutableArray copy] autorelease]; }  @end