Question

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What is “->” in Objective C?

beginner question here. Im looking through this intro to the objective c runtime (http://mikeash.com/pyblog/friday-qa-2009-03-13-intro-to-the-objective-c-runtime.html) and I see this funky syntax with a ->. Can’t seem to find an explanation on what that means.

Easy points anyone?

Thanks!

Answer 1

That is actually C syntax. It’s used to access a field (variable) of a pointer to a struct.

When you have a pointer, you have to use the * syntax to dereference it:

int var = 1;   // regular int variable
int *ptr = &var;  // pointer to that variable
int sum = (*ptr) + 3;   // if you want to use it regularly, you have to dereference it first.

Now, if this pointer happens to be a struct pointer, it can become ugly:

// Define and typedef a struct.
typedef struct {
    int num1;
    int num2; 
} MyStruct;

MyStruct myStruct = (MyStruct){1, 2};   // Regular struct.
MyStruct *pointer = &myStruct;          // Pointer to that struct.
int sum = (*pointer).num1 + (*pointer).num2;   // The ugly part.
int niceSum = pointer->num1 + pointer->num2;   // Same thing with cleaner code.