objective-C中如何判斷一個類中有沒有定義某個方法

C#中可以通過反射分析中繼資料來解決這個問題，範例程式碼如下：

using System;using System.Reflection;namespace Hello{    class Program    {        static void Main(string[] args)        {            if (IsMethodDefined(typeof(Utils), "HelloWorld"))            {                Console.WriteLine("Utils類中有方法HelloWorld");            }            else             {                Console.WriteLine("Utils類中沒有方法HelloWorld");            }            Console.ReadKey();        }                    /// <summary>        /// 判斷一個類中有無"指定名稱"的方法        /// </summary>        /// <param name="type"></param>        /// <param name="methodName"></param>        /// <returns></returns>        static bool IsMethodDefined(Type type,string methodName)         {            bool result = false;            foreach (MemberInfo m in type.GetMembers())            {                if (m.Name == methodName)                 {                    result = true;                    break;                }            }            return result;        }    }    public static class Utils    {        public static void HelloWorld()        {            Console.WriteLine("Hello World!");        }    }}

在obj-C中，則是通過選取器selector來判斷的

Sampe.h

#import <Foundation/Foundation.h>@interface Sample : NSObject {}-(void) print:(NSString*) msg;@end

Sample.m

#import "Sample.h"@implementation Sample-(void) print:(NSString*) msg{NSLog(@"%@",msg);}@end

main函數:

#import <Foundation/Foundation.h>#import "Sample.h"int main (int argc, const char * argv[]) {    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];Sample *s = [Sample new];if ([s respondsToSelector:@selector(print:)]) //這一行就是判斷執行個體s中有沒有方法print{[s print:@"Hello World"];}else{NSLog(@"%@",@"Sample類中沒有定義方法print");}[s release];    [pool drain];    return 0;}