The const modifier in Objective-c

Question

1, Please see the following code:

const UIView *view = [[UIView alloc] init];
view.tag = 2;

2,In my mind, the "const" meaning the variable can't be changed.
3, So I think I can't change the content of the object which "view" point to,but I can change the view.tag, I don't know why.

score 5 · Accepted Answer · edited May 23 '17 at 12:14

5

The correct usage would be UIView *const view = [[UIView alloc] init];

You can't change the content of view but you can always change the content of the object which view holds

Rest is explained in this question : What is the difference between const int*, const int * const, and int const *?

Why you are able to change the tag is because it is defined as

@property(nonatomic) NSInteger tag; // default is 0

It's not defined as constant(readonly) thus you are able to change its tag. If you want that content of the object should not change then in that case you have to change the definition of that class and make their ivar as const or readonly in case of properties.

edited May 23 '17 at 12:14

Community

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answered Oct 26 '15 at 11:49

Inder Kumar Rathore

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1,Actually, I think there is no approach to change the content of the object. – huixing Oct 26 '15 at 11:56
I can change the pointer or the content the object holds only. – huixing Oct 26 '15 at 11:57

The const modifier in Objective-c

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