Boxing with Objective-C

gistfile1.m

// Public domain. (You're welcome.)

/// BOX(expr)
///
/// Macro. Box simple things like `CGPoint` or `CGRect` into an `NSValue`.
///
/// (Compare with the use of `@` in `@YES`, @123, @"abc" or `@(1 + 2)`.)

#define BOX(expr) ({ __typeof__(expr) _box_expr = (expr); \
    [NSValue valueWithBytes:&_box_expr objCType:@encode(__typeof__(expr))]; })


// --- Example -----------------------------------------------------------------

CGPoint point = CGPointMake(10, 20);
CGSize size = CGSizeMake(30, 40);
CGRect rect = CGRectMake(10, 20, 30, 40);
UIEdgeInsets inset = UIEdgeInsetsMake(1, 2, 3, 4);

NSValue *pointValue = BOX(point);  // = [NSValue valueWithCGPoint:point];
NSValue *sizeValue  = BOX(size);   // = [NSValue valueWithCGSize:size];
NSValue *rectValue  = BOX(rect);   // = [NSValue valueWithCGRect:rect];
NSValue *insetValue = BOX(inset);  // = [NSValue valueWithUIEdgeInsets:inset];


// Boxed things can be put into an array.

NSArray *values1 = @[pointValue, sizeValue, rectValue, insetValue];
NSArray *values2 = @[BOX(point), BOX(size), BOX(rect), BOX(inset)];


// Works for temporaries as well.

NSValue *pointValueFromExpression = BOX(CGPointMake(10, 20));


// Practical for logging things with NSLog:

CGRect rect = CGRectMake(10, 20, 30, 40);
NSLog(@"rect: %@", BOX(rect));  // -> rect: NSRect: {{10, 20}, {30, 40}}


// --- But watch out, you can shoot yourself to the foot with this: ------------

NSValue *badValue = BOX(@[]); // ***Not even a warning!***

// Improvements to fix this, or any other issue are very welcome!

For the Objective-C++'ers out there, try out https://gist.github.com/539747 as well.