Possible to initialize an array after the declaration in C?

Question

Is there a way to declare a variable like this before actually initializing it?

    CGFloat components[8] = {         0.0, 0.0, 0.0, 0.0,         0.0, 0.0, 0.0, 0.15     }; 

I'd like it declared something like this (except this doesn't work):

    CGFloat components[8];     components[8] = {         0.0, 0.0, 0.0, 0.0,         0.0, 0.0, 0.0, 0.15     }; 

Answer 1

You cannot assign to arrays so basically you cannot do what you propose but in C99 you can do this:

CGFloat *components; components = (CGFloat [8]) {     0.0, 0.0, 0.0, 0.0,     0.0, 0.0, 0.0, 0.15 }; 

the ( ){ } operator is called the compound literal operator. It is a C99 feature.

Note that in this example components is declared as a pointer and not as an array.

Answer 2

If you wrap up your array in a struct, it becomes assignable.

typedef struct {     CGFloat c[8]; } Components;   // declare and initialise in one go: Components comps = {     0.0, 0.0, 0.0, 0.0,     0.0, 0.0, 0.0, 0.15 };   // declare and then assign: Components comps; comps = (Components){     0.0, 0.0, 0.0, 0.0,     0.0, 0.0, 0.0, 0.15 };   // To access elements: comps.c[3] = 0.04; 

If you use this approach, you can also return Components structs from methods, which means you can create functions to initialise and assign to the struct, for example:

Components comps = SomeFunction(inputData);  DoSomethingWithComponents(comps);  comps = GetSomeOtherComps(moreInput);  // etc.