Question

Could anyone tell me the difference between

NSString* string;

And

NSString* string = [NSString string];

Answer 1

Just like in C,

NSString *string;

declares the variable (pointer) string but gives it no value. This means you can’t use the variable until you’ve initialized it, for example by doing string = @"foo";.

Note:

• If this is an instance variable it actually will be initialized automatically — to nil.
• If you use the variable somewhere in your code without initializing it in every possible branch (if conditions, etc.) then the compiler will complain. To avoid this you could just set it to an empty string or nil to start with.

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The line

NSString *string = [NSString string];

uses the +string method of the NSString class to create an empty string. You could also use @"".

(Further note: I recommend using NSString *string instead of NSString* string because the former hides a syntax idiosyncrasy: NSString *string1, *string2; is the correct way to declare multiple pointer variables on one line.)