objective-c，反射

objective-c中提供类似JAVA的反射特性，给出基本例子如下：

#import <Foundation/Foundation.h>

@interface ClassA : NSObject{
    int _id1;
    int _id2;
    int _id3;
}

@property int _id1;
@property int _id2;
@property int _id3;

-(void) setId1:(int)id1 andId2:(int)id2 andId3:(int)id3;
-(void) doMethod1;
-(void) doMethod2;
-(void) doMethod3;

@end


@implementation ClassA

@synthesize _id1,_id2,_id3;

-(void) setId1:(int)id1 andId2:(int)id2 andId3:(int)id3{
    _id1 = id1;
    _id2 = id2;
    _id3 = id3;
}

-(void) doMethod1{
    NSLog(@"%i", self._id1);}

-(void) doMethod2{
    NSLog(@"%i", self._id2);}

-(void) doMethod3{
    NSLog(@"%i", self._id3);}

@end

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        Class class = NSClassFromString(@"ClassA"); //通过字符串获取CLASS
        NSLog(@"%@", [class className]); //打印class的名称，在oc中class是一个结构体
        NSObject *tmp;
        
        SEL sel1 = @selector(doMethod2); //SEL对应选择一个方法
        SEL sel2 = NSSelectorFromString(@"doMethod1");
        SEL sel3 = NSSelectorFromString(@"setId1:andId2:andId3:");
        tmp = [[class alloc]init];
        
 //判断实例中是否包含这个方法，类似的还有是否属于某一个类等接口
        if([tmp respondsToSelector:sel3] == YES) {
            
  //oc中反射的基本函数performSelector不支持传入基本参数，如int，以及多个参数，解决的方法有很多种，
            //比如可以在设计中就将参数进行封装，下面这个方法是通过NSInvocation传入参数；

            NSInvocation *inv = [NSInvocation invocationWithMethodSignature:
                                 [tmp methodSignatureForSelector:sel3]];
            
            [inv setSelector:sel3];
            [inv setTarget:tmp];
            
            //arguments 0 and 1 are self and _cmd respectively, automatically set by NSInvocation
            int input1 = 1;
            int input2 = 2;
            int input3 = 3;
            
            [inv setArgument:&(input1)  atIndex:2]; //第一个参数传入
            [inv setArgument:&(input2)  atIndex:3]; //第二个参数传入
            [inv setArgument:&(input3)  atIndex:4]; //第三个参数传入
            [inv invoke];
        }
        
        [tmp performSelector:sel1 withObject:nil]; //执行该方法
        
        if([tmp　respondsToSelector:sel2] == YES) {
            [tmp performSelector:sel2 withObject:nil];
        }
        
    }
    return 0;
}