Swap a subview with another view, copying the constraints from the first to the second.

UIView+SubviewReplacing.m

@implementation UIView (SubviewReplacing)

- (void)replaceSubview:(UIView *)subview withView:(UIView *)newView
{
	newView.frame = subview.frame;
	[self addSubview:newView];
	for (NSLayoutConstraint *constraint in [subview.constraints arrayByAddingObjectsFromArray:self.constraints]) {
		id firstItem = nil;
		id secondItem = nil;
		if (constraint.firstItem == subview) {
			firstItem = newView;
			secondItem = constraint.secondItem;
		}
		else if (constraint.secondItem == subview) {
			firstItem = constraint.firstItem;
			secondItem = newView;
		}
		if (firstItem) {
			NSLayoutConstraint *newConstraint = [NSLayoutConstraint constraintWithItem:firstItem attribute:constraint.firstAttribute relatedBy:constraint.relation toItem:secondItem attribute:constraint.secondAttribute multiplier:constraint.multiplier constant:constraint.constant];
			if (nil == secondItem) {
				[self addConstraint:newConstraint];
			}
			else {
				[newView addConstraint:newConstraint];
			}
		}
	}
	[subview removeFromSuperview];
	subview = newView;
}

@end