Question

This is really simple but driving me nuts.

I am trying to implement a simple function in my Objective-C code. When I write this,

NSInteger Sort_Function(id id1, id id2, void *context) {

}

I get an error that a semi-colon was expected at the end of the declaration. However, I’ve seen this type of syntax in many, many examples. What could I possibly be doing wrong? If it matters, this is an iOS app and the function is nested in an if clause. Thanks in advance.

Answer 1

The function definition — this snippet you posted — is “nested in a if clause”? That’s unfortunately illegal in C (and Obj-C by extension) — all function declarations and definitions have to be at the top level of the file. Inside an @implementation section is also an option:

// Start of file

// Declaration or definition valid here
void my_func(void);    // Declaration
void my_other_func(void);
void my_third_func(void);

void my_func(void) {    // Definition
    return;
}

@implementation MyClass

// Definition also valid here
void my_other_func(void) {
    return;
}

- (void) myMethod {
    if( YES ){
        void my_third_func(void) {    // Invalid here
            return;
        }
    }
}

@end

Is it possible you’re confusing the function syntax with block syntax?

// The caret indicates definition of a block, sort of an anonymous function
int (^myBlock)(int);
myBlock = ^int (int my_int) {
    return my_int;
};