A performIfResponds proxy for NSObject. Never use -respondsToSelector again.

For example, this:

if([self.delegate respondsToSelector:@selector(fooForBar:]) {
	foo = [self.delegate fooForBar:self]:
}

becomes this:

foo = [[self.delegate performOrReturn:nil] fooForBar:self]:

See bou.io/PerformIfResponds for more details.