反射实现NSCodingProtocol 帮助类

// .h文件
#import <Foundation/Foundation.h>
@interface NSCodingProtocolHelper : NSObject
+(void)encodeWithCoder:(NSCoder *)aCoder andObj:(id)obj;
+(id)initWithCoder:(NSCoder *)aDecoder andObj:(id)obj;

@end

// .m文件
#import "NSCodingProtocolHelper.h"
#import <objc/runtime.h> //反射需要用到的头文件

@implementation NSCodingProtocolHelper
+(void)encodeWithCoder:(NSCoder *)aCoder andObj:(id)obj
{
    unsigned int outCount;
    objc_property_t *properties = class_copyPropertyList([obj class], &outCount);
    for (int i = 0; i < outCount; i++) {
        objc_property_t *thisProperty = properties + i;
        NSString *propertyName = [NSString stringWithUTF8String:property_getName(*thisProperty)];
        [aCoder encodeObject:[obj valueForKey:propertyName] forKey:propertyName];
    }
}

+(id)initWithCoder:(NSCoder *)aDecoder andObj:(id)obj
{
    unsigned int outCount;
    objc_property_t *properties = class_copyPropertyList([obj class], &outCount);
    for (int i = 0; i < outCount; i++) {
        objc_property_t *thisProperty = properties + i;
        NSString *propertyName = [NSString stringWithUTF8String:property_getName(*thisProperty)];
        [obj setValue:[aDecoder decodeObjectForKey:propertyName] forKey:propertyName];
    }
    return obj;
}
@end

使用方法：

在要实现NSCodingProtocle的类中重写 initWithCoder: 和encodeWithCoder: 方法，

例如：

-(void) encodeWithCoder:(NSCoder *)aCoder
{
    [NSCodingProtocolHelper encodeWithCoder:aCoder andObj:self];
    
}
-(id)initWithCoder:(NSCoder *)aDecoder
{
    return [NSCodingProtocolHelper initWithCoder:aDecoder andObj:selfl];
}

property_getAttributes 方法可以获得属性，

[NSString stringWithUTF8String:property_getAttributes(*property)]得到类似 

Ti,N,V_uid

或者 

T@"NSString",C,N,V_name

这样的字符串，通过截取第二个字符可以判断属性的类型，@代表对象。