Read-only outlet?
Let's say I have a class. I would like to declare a property in the following way:
- From outside of the class it should be read-only if accessed programmatically;
- It should be possible to set the value f开发者_C百科rom the Interface Builder using an outlet;
- (From inside the class it should be writable, but I know how to do it).
The "solution" I came up with is to write a one-time setter:
- (void) setA: (ClassA *)a {
if (aHaveBeenSet)
return;
else {
// do what a setter have to do
aHaveBeenSet == YES;
}
}
But this setter still can be called from the code (though only once in effect), so it's not quite a solution.
Another way is to mark the ivar as IBOutlet and make the property readonly
like this:
@interface MyClass : NSObject {
IBOutlet ClassA *a;
}
@property (readonly) ClassA *a;
@end
But according to this answer, it's a poor style and makes memory management unclear.
Any ideas?
Someone correct me if I'm wrong, but I think the NIB loading mechanism checks for a setter method only when instantiating a .nib file at runtime. So that means you could declare your public property as readonly but write a "private" setter in your .m file:
// MyClass.h
@property (readonly, retain) IBOutlet ClassA *a;
// MyClass.m
@interface MyClass ()
@property (readwrite, retain) ClassA *a;
@end
@implementation MyClass
@synthesize a;
...
@end
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