CODEWITHSUNDEEP
objective-c
b1ade
b1ade

Reputation: 53

What is the difference between NSString* mystring and NSString *mystring

I've come across several examples which declares classes in the header differently like

NSString* mystring;

or

NSString *mystring;

What's the difference?

Upvotes: 5

Views: 752

Answers (9)

paxdiablo
paxdiablo

Reputation: 881403

Those are three totally distinct lexical elements and the amount of whitespace in-between them is totally irrelevant. These are all equivalent in terms of what the compiler generates:

NSString*x;
NSString *x;
NSString* x;
NSString * x;
NSString                 *                 x;
NSString /* comment here */ * /* and another */ x;

I prefer the NSString *x variation since the pointer specifier belongs to the variable, not the type. By that, I mean that both of these:

int *x, y;
int* x, y;

create an integer pointer called x and an integer called y, not two integer pointers.

Upvotes: 15

Jasper Blues
Jasper Blues

Reputation: 28756

There's no difference. It's a matter of preference and style.

  • Here comes a variable that's of type NSString pointer (NSString* mystring)
  • Here comes a variable of type NSString that's a pointer (NSString *mystring)

    • Advantage of the first approach:

    When coding to protocols, there's no issue with some variables having a star and some not. Example:

    NSString*        _myString
id<SomeProtocol> _collaborator

    versus (more confusing):

    NString          *_myString
id<SomeProtocol> _collaborator

    Drawback to this approach: (as pointed out)

    //Only the first is a pointer. 
NSString* _myString, _anotherString

    Modern OO languages (like Java) tend to discourage multiple variables on one line: http://java.sun.com/docs/codeconv/html/CodeConventions.doc5.html#2991

    Upvotes: 0

    David
    David

    Reputation: 326

    In C (and Objective-C, as a superset of C), placement of the * is merely a matter of style.

    I'd recommend checking out the relevant section from Google's style guide.

    Upvotes: 0

    bvanderveen
    bvanderveen

    Reputation: 763

    There is no difference. It's a matter of style.

    In Objective-C, you can pretty much think of the star as part of the 'type' of the variable.

    However, the compiler interprets the star as "treat this variable as a pointer to the declared type" (in this case NSString). Where it gets interesting is defining multiple variables at once:

    NSString *myString, *yourString;

    You must use the star on each variable.

    Upvotes: 3

    John Parker
    John Parker

    Reputation: 54445

    None whatsoever - it's a personal preference as to whether you think...

    1. Here comes a variable that's of type NSString pointer (NSString* mystring)

      or

    2. Here comes a variable of type NSString that's a pointer (NSString *mystring)

    ...is more legible. That said, as long as you're consistent it isn't something you should loose sleep over.

    Upvotes: 0

    StuartLC
    StuartLC

    Reputation: 107247

    Is preference, and is useful if you declare multiple variables in the same line, viz

    NSString* mystring1, mystring2;  // Misleading, mystring2 is not a *

NSString *mystring1, mystring2;  // Is more clear

    Upvotes: 1

    Micha&#235;l
    Micha&#235;l

    Reputation: 6734

    There is no differences in reality.

    Upvotes: 0

    Fox32
    Fox32

    Reputation: 13560

    Nothing, it isn't even important to have space between them. You can even write NSString*mystring.

    Upvotes: 0

    Matthias Bauch
    Matthias Bauch

    Reputation: 90117

    no difference, just coding style preference.

    Upvotes: 0

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