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I have a C-array of CGPoint that I want to declare in the header file .h.

CGPoint checkPoint[8];

But when I try to give it a value in .m:

checkPoint[8] = { //<-- Error Here
    CGPointMake(0, -10),
    CGPointMake(10, 0),
    CGPointMake(0, 10),
    CGPointMake(-10, 0),
    CGPointMake(-10, -10),
    CGPointMake(10, -10),
    CGPointMake(10, 10),
    CGPointMake(-10, 10)
};

It gives me an error pointing at the first opening bracket: Expected expression

Im not very used with C-arrays, how is the correct way of doing this?

EDIT

I have tried with extern in the header file, but I get this error message: Type name does not allow storage class to be specified.

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Please show the section of the header where you declare extern CGPoint checkPoint[8]; It must be done outside any type / interface declaration, otherwise extern would not be valid. –  dasblinkenlight Nov 8 at 10:50
 
Oh, I didn't know that it had to be outside of the @interface, I don't get that error anymore, but I still get the error when I try giving it a value. –  Arbitur Nov 8 at 10:55
 
That too needs to be outside any @implementation block in a .m file, and it may not call CGPointMake. –  dasblinkenlight Nov 8 at 10:57
 
xD Im so unused to these types of arrays. Thanks man it works like I want now, I accept your answer and you can add that it needs to be outside of the interface and implementation so other people can find it faster ;) –  Arbitur Nov 8 at 11:04

2 Answers

up vote 3 down vote accepted

You need to add extern to the declaration in the header:

extern CGPoint checkPoint[8];

This would make it a declaration, rather than a declaration/definition. Note that the definition wouldn't compile because of calls to CGPointMake in the initializer (must be compile-time constant, but CGPointMake is a function).

You can replace CGPointMake with {.x= 0, .y=-10} style of initializer, like this:

checkPoint[8] = { //<-- Error Here
    {.x=0,   .y=-10},
    {.x=10,  .y=0},
    {.x=0,   .y=10},
    {.x=-10, .y=0},
    {.x=-10, .y=-10},
    {.x=10,  .y=-10},
    {.x=10,  .y=10},
    {.x=-10, .y=10}
};

Note : (in response to a thread of comments to question)

extern is used for declaring global variables. They do not belong to any class, so their declaration needs to be outside an @interface, and their definition needs to be outside the @implementation block.

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I've tried that already, sorry for not including it in the question, when I use the extern I get an error message: Type name does not allow storage class to be specified. –  Arbitur Nov 8 at 10:46
 
@Arbitur Are you trying to declare the extern variable as an instance variable for a class? There are four or five SO questions relating to that error message and they all relate to putting extern or static on an instance variable declaration. –  JeremyP Nov 8 at 12:20
up vote 2 down vote

Declare it as extern CGPoint checkPoint[8] in the header, and then in one source file you can initialise it as CGPoint checkPoint[8] = { { 0.0f, -10.0f }, { 10.0f, 0.0f }, … };

Without the extern you would be defining it anew in every file that includes the header. The initialisers also need to be compile-time constants.

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