Runtime--将信息对象归档解档

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当我们需要将一个对象进行归档时，都要让该对象的类遵守NSCoding协议，再实现归档和接档方法。例如有一个Person类，该类有两个成员变量

  @property (nonatomic,copy) NSString *name; 
 @property (nonatomic,assign)  int  age; 
 

两个协议的实现方法如下

/***  将对象写入某个文件时需要调用，在该方法中说明哪些属性需要存储*/
- (void)encodeWithCoder:(NSCoder *)encoder
{[encoder encodeObject:self.name forKey:@"name"];[encoder encodeInt:self.age forKey:@"age"];
}/***  从文件中解析对象时会调用，在该方法中解析对象的属性*/
- (id)initWithCoder:(NSCoder *)decoder
{if (self = [super init]) {// 解析之后要赋值给属性_name = [decoder decodeObjectForKey:@"name"];_age = [decoder decodeIntForKey:@"age"];}return self;
}

但当该类拥有上百个属性时，那将会花费更多的功夫在重复代码上，所以使用运行时机制截取类的成员变量，进行赋值

例如有一个狗类Dog和它的父类动物类Animal

狗类的成员变量有

@property (nonatomic,copy) NSString *name;
@property (nonatomic,assign) int age;

动物类的成员变量有

@property (nonatomic,assign) double weight;

当我们需要将狗对象进行归档时，可以在类中这样重写归档和解档方法

- (id)initWithCoder:(NSCoder *)aDecoder
{if (self = [super init]) {Class c = self.class;// 截取类和父类的成员变量while (c && c != [NSObject class]) {unsigned int count = 0;Ivar *ivars = class_copyIvarList(c, &count);for (int i = 0; i < count; i++) {NSString *key = [NSString stringWithUTF8String:ivar_getName(ivars[i])];id value = [aDecoder decodeObjectForKey:key];[self setValue:value forKey:key];}// 获得c的父类c = [c superclass];free(ivar);}}return self;
}- (void)encodeWithCoder:(NSCoder *)aCoder
{Class c = self.class;// 截取类和父类的成员变量while (c && c != [NSObject class]) {unsigned int count = 0;Ivar *ivars = class_copyIvarList(c, &count);for (int i = 0; i < count; i++) {Ivar ivar = ivars[i];NSString *key = [NSString stringWithUTF8String:ivar_getName(ivar)];id value = [self valueForKey:key];[aCoder encodeObject:value forKey:key];}c = [c superclass];// 释放内存
        free(ivar);}}

代码测试：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{CXDog *d = [[CXDogalloc] init];d.name = @"cx";d.age = 12;d.weight = 1.55;// 将对象归档[NSKeyedArchiverarchiveRootObject:d toFile:@"/Users/c_xie/Desktop/wj.xxoo"];// 将对象解档CXDog *dog = [NSKeyedUnarchiverunarchiveObjectWithFile:@"/Users/c_xie/Desktop/wj.xxoo"];NSLog(@"%@,%d,%f",dog.name,dog.age,d.weight);}