对象归档与KVC KVO

Posted 2021-06-28 亚洲小炫风

对象归档是一个过程,即某种格式来保存一个或者多个对象,以便以后还原这些对象
在其他语言中,对象归档也叫对象序列化
对象归档包括两个过程
--将对象状态写入文件
--从文件中写入对象

自定义对象只有实现NSCoding协议(ios 13需要支持NSSecureCoding)才能支持归档操作
-initWithCoder:从文件中还原对象(解档)
-encodeWithCoder: 将对象归档

User.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface User : NSObject<NSSecureCoding>

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

NS_ASSUME_NONNULL_END

User.m

#import "User.h"

@implementation User

//解档
- (instancetype)initWithCoder:(NSCoder *)coder
{
    self = [super init];
    if (self) {
        self.name =[coder decodeObjectForKey:@"name"];
        self.age = [coder decodeIntForKey:@"age"];
    }
    return self;
}
+ (BOOL)supportsSecureCoding
{
    return true;
}

- (void)encodeWithCoder:(NSCoder *)coder
{
    [coder encodeObject:self.name forKey:@"name"];
    [coder encodeInt:_age forKey:@"age"];
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"name:%@ age:%d", _name,_age];
}

@end

 

 User *u=[[User alloc] init];
    u.name=@"张三";
    u.age=14;
    
    NSError *error;
    
    NSData *data=[NSKeyedArchiver archivedDataWithRootObject:u requiringSecureCoding:YES error:&error];
    if(error!=nil)
    {
        NSLog(@"======>归档错误:%@",error);
        return;
    }
    
    NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:@"test.archiver"];
    //创建文件
    [[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil];
    //写入
    [data writeToFile:path atomically:YES];
 
    
    
    
  
    //解档
    NSData *data2=[NSData dataWithContentsOfFile:path];
 
    error=nil;
    User *unarchiverUser=(User *)[NSKeyedUnarchiver unarchivedObjectOfClass:[User class] fromData:data2 error:&error];
    if(error!=nil)
    {
        NSLog(@"======>解档错误:%@",error);
    }
    NSLog(@"=====>unarchiverUser:%@",unarchiverUser);

将多个对象归档在同一个文件中

    NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:@"test22.archiver"];
    
   //将多个对象归档在同一个文件中
    User *user=[[User alloc] init];
    user.name=@"张三";
    user.age=24;
    
    User *user2=[User new];
    user2.name=@"李四";
    user2.age=25;
    

    NSKeyedArchiver *archiver=[[NSKeyedArchiver alloc] initRequiringSecureCoding:NO];
    [archiver encodeObject:user forKey:@"user"];
    [archiver encodeObject:user2 forKey:@"user2"];
    
    [archiver.encodedData writeToFile:path atomically:YES];
    
    [archiver finishEncoding];


    
  

    
    NSData *data=[NSData dataWithContentsOfFile:path];
    NSKeyedUnarchiver *unarchiver=[[NSKeyedUnarchiver alloc] initForReadingFromData:data error:nil];
    [unarchiver setRequiresSecureCoding:NO];
    User *unarchiverUser=[unarchiver decodeObjectForKey:@"user"];
    User *unarchiverUser2=[unarchiver decodeObjectForKey:@"user2"];
    NSLog(@"======>test unarchiverUser:%@",unarchiverUser);
    NSLog(@"======>test unarchiverUser2:%@",unarchiverUser2);