NSCoding Protocol Reference

encodeWithCoder:

Encodes the receiver using a given archiver. (required)

- (void)encodeWithCoder:(NSCoder *)encoder

Parameters

encoder

An archiver object.

Availability

• Available in iOS 2.0 and later.

Declared In

NSObject.h

initWithCoder:

Returns an object initialized from data in a given unarchiver.(required)

- (id)initWithCoder:(NSCoder *)decoder

Parameters

decoder

An unarchiver object.

Return Value

self, initialized using the datain decoder.

Availability

• Available in iOS 2.0 and later.

Declared In

NSObject.h

NSCoding协议中只有两个方法，都是require的方法，一个是把本身的类进行转码，一个是逆转换成类对象，返回一个对象，我们实战一下这个协议的用法，看看是否好用，首先写一个自定义Student类:

@interfaceStudent : NSObject<NSCoding>

@property (nonatomic, retain) NSString *name;

@property (nonatomic, retain) NSString *ID;

-(Student *)initWithName :(NSString*)newName 

                 and : (NSString *)newID;

@end

Student类需要实现协议NSCoding，.m文件中是这样的:

 

@implementationStudent

@synthesize name = _name,ID = _ID;

 

//初始化学生类

-(Student *)initWithName:(NSString *)newName and:(NSString *)newID{

   self = [super init];

   if (self) {

       self.name = newName;

       self.ID= newID;

    }

   return self;

}

//学生类内部的两个属性变量分别转码

-(void)encodeWithCoder:(NSCoder *)aCoder{

   [aCoder encodeObject:self.name forKey:@"name"];

   [aCoder encodeObject:self.IDforKey:@"ID"];

}

//分别把两个属性变量根据关键字进行逆转码，最后返回一个Student类的对象

-(id)initWithCoder:(NSCoder *)aDecoder{

   if (self = [super init]) {

       self.name = [aDecoder decodeObjectForKey:@"name"];

       self.ID= [aDecoder decodeObjectForKey:@"ID"];

    }

   return self;

}

@end

自定义类Student实现了NSCoding协议以后，就可以进行归档转换了，具体实现：

 

   Student *stu1 = [[Student alloc]initWithName:@"124" and:@"111"];//学生对象stu1

   Student *stu2 = [[Student alloc]initWithName:@"223" and:@"222"];//学生对象stu2

   NSArray *stuArray =[NSArray arrayWithObjects:stu1,stu2, nil];//学生对象数组，里面包含stu1和stu2

   NSData *stuData = [NSKeyedArchiver archivedDataWithRootObject:stuArray];//归档

   NSLog(@"data = %@",stuData);

   NSArray *stuArray2 =[NSKeyedUnarchiver unarchiveObjectWithData:stuData];//逆归档

   NSLog(@"array2 = %@",stuArray2);