Sending nil to CGPoint type parameter - objective-c

Question

Suppose I have this method:
- (void)placeView:(UIView*)theView withCenterIn:(CGPoint)centerPoint;
So I pass the view and a point to te the view's center.
But it happens that I do not need to specify the center, just the view.
Passing "nil" leads to error.
Please, suggest how to skip passing the center point.
Keep in mind that I need to use that method like this:
- (void)placeView:(UIView*)theView withCenterIn:(CGPoint)centerPoint{
if(centerPoint == nil){//and I understand that it's a wrong comparison, as I cannot pass "nil" to CGPoint
//set a random center point
}
else{
//set that view to the specified point
}
}
Thanks in advance

Answer 1

You can't use nil as a "no point" indicator, because it is only for objects, and CGPoint is a struct. (As dasblinkenlight has already said.)
In my geometry library, I've defined a "null" CGPoint to use as a "no point" placeholder, and a function to test for it. Since the components of a CGPoint are CGFloats, and floats have a "invalid value" representation already -- NAN, defined in math.h -- I think that's the best thing to use:
// Get NAN definition
#include <math.h>
const CGPoint WSSCGPointNull = {(CGFloat)NAN, (CGFloat)NAN};
BOOL WSSCGPointIsNull( CGPoint point ){
return isnan(point.x) && isnan(point.y);
}

Answer 2

CGPoint is a C struct, you cannot pass nil for it. You can create a separate method that does not take the unnecessary CGPoint, and get rid of your if statement, like this:
- (void)placeView:(UIView*)theView withCenterIn:(CGPoint)centerPoint{
//set that view to the specified point
}
- (void)placeView:(UIView*)theView {
//set a random center point
}
If you insist on keeping one method, you could designate one point as "special" (say, CGMakePoint(CGFLOAT_MAX, CGFLOAT_MAX)), wrap it in a #define, and use instead of nil.
Yet another solution would be to wrap your CGPoint in NSValue:
NSValue *v = [NSValue withPoint:CGMakePoint(12, 34)];
CGPoint p = [v pointValue];