分配NSInteger *

Question

I'm sure I'm missing something obvious but I'd like to create an instance of a NSInteger pointer in Objective C.

-(NSInteger*) getIntegerPointer{
  NSInteger  refValue = 0;
  NSInteger* theReturn = &refValue;
  return theReturn;
}

When I call this function theReturn is nil, but is valid within the function with the debugger.

Any suggestions? I do not want to change theReturn to NSInteger.

Answer 1

The variable refValue is a local variable, which means that it will be on the stack while the -getIntegerPointer method is executing. As soon as that method returns, the variable will go away (be popped off the stack), so it's address is no longer meaningful.

If you want to return a valid pointer, you have to allocate the memory for the thing being pointed to, like this:

-(NSInteger*) getIntegerPointer{
    NSInteger  refValue = 0;
    NSInteger* theReturn = malloc (sizeof(NSInteger));
    *theReturn = refValue;
    return theReturn;
}