원형은..

NSSelectorFromString(<#NSString *Selector Name#>)

해당 함수(메소드)의 유효성을 확인하는 코드

SEL selector = NSSelectorFromString(@"placeToDownWithPos:shipSize:");
if ([self respondsToSelector:selector]) {
    NSLog(@"respondsToSelector");
}

실행까지는 이렇게 하면 됨 ㅋㅋ

NSString *methodString = @"agreeOmClause";
SEL selector = NSSelectorFromString(methodString);
if ([self respondsToSelector:selector]) {
    [self performSelector:selector withObject:nil afterDelay:0.0];
}

[출처] http://stackoverflow.com/questions/22585912/nsselectorfromstring-does-not-work