Declaring NSString constants

Question

Right now I am using the following way declare constants in header file:

static NSString *const RSMaxNumberOfIndustiresKey = @"MaxNumberOfIndustries";

Is it correct? I read Constants in Objective-C question but I really don't know if I really need to declare constant in 2 different places using FOUNDATION_EXPORT.

score 1 · Accepted Answer · answered Oct 31 '14 at 14:55

1

No. You should use the following in Constants.h:

extern NSString *const RSMaxNumberOfIndustiresKey;

and this in Constants.m:

NSString *const RSMaxNumberOfIndustiresKey = @"MaxNumberOfIndustries";

(i.e. add an implementation file simply to hold the single instance of the string constants).

Using your current method means there is a copy of each string within every file that includes that header.

answered Oct 31 '14 at 14:55

trojanfoe

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String literals are not copied in memory in Objective-C. – Ian MacDonald Oct 31 '14 at 14:57
@IanMacDonald Yeah it's not the end of the world with string constants, but once other types of objects are used, it will become a problem. – trojanfoe Oct 31 '14 at 14:58
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@IanMacDonald You will have a variable collision once you import the header from two different places. – Sulthan Oct 31 '14 at 14:58

Declaring NSString constants

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