第四章 Runtime应用：实现NSCoding的自动归档和自动解档

向右看齐 2022-05-21 12:22 190阅读 0赞

用`runtime`提供的函数遍历Model自身所有属性，并对属性进行`encode`和`decode`操作。  
通常系统自带的数据类型，如：字典NSDictionary，数组NSArray，字符串NSString，布尔数据BOOL，数字对象NSNumber，NSData，NSDate等可以直接进行存储操作；但是自定义的数据类型，如果直接进行存储操作时，则会抛出异常，这时候就需要进行归档、解档处理。

示例代码

#import <Foundation/Foundation.h>
    
    @interface Person : NSObject
    
    @property (nonatomic, strong) NSString *name;
    @property (nonatomic, strong) NSNumber *age;
    @property (nonatomic, strong) NSString *address;
    @property (nonatomic, strong) NSString *company;
    @property (nonatomic, strong) NSString *job;
    
    @end

#import "Person.h"
    #import <objc/runtime.h>
    
    @implementation Person
    
    - (id)initWithCoder:(NSCoder *)aDecoder
    {
        if (self = [super init])
        {
            unsigned int outCount;
            Ivar *ivars = class_copyIvarList([self class], &outCount);
            for (int i = 0; i < outCount; i ++)
            {
                Ivar ivar = ivars[i];
                NSString *key = [NSString stringWithUTF8String:ivar_getName(ivar)];
                [self setValue:[aDecoder decodeObjectForKey:key] forKey:key];
            }
        }
        return self;
    }
    
    - (void)encodeWithCoder:(NSCoder *)aCoder
    {
        unsigned int outCount;
        Ivar *ivars = class_copyIvarList([self class], &outCount);
        for (int i = 0; i < outCount; i ++)
        {
            Ivar ivar = ivars[i];
            NSString *key = [NSString stringWithUTF8String:ivar_getName(ivar)];
            [aCoder encodeObject:[self valueForKey:key] forKey:key];
        }
    }
    
    @end

使用

// 自动归档/解档
    NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:@"PersonInfo"];
    if (data) { // 解档使用 Person *person = [NSKeyedUnarchiver unarchiveObjectWithData:data]; NSLog(@"name: %@", person.name); } else { Person *person = [Person new]; person.name = @"devZhang"; person.age = @(35); person.company = @"ShengXue"; person.job = @"iOSDev"; person.address = @"龙岗坂田国际中心"; // 归档存储 data = [NSKeyedArchiver archivedDataWithRootObject:person]; [[NSUserDefaults standardUserDefaults] setObject:data forKey:@"PersonInfo"]; }

未进行归档、解档时报错

// 归档错误
    Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Person encodeWithCoder:]: unrecognized selector sent to instance 0x600000450d40'
    
    // 解档错误
    Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Person initWithCoder:]: unrecognized selector sent to instance 0x60000005d760'

使用自动归档、解档后，自定义类型数据处理正常

2018-07-07 00:26:20.023737+0800 DemoRuntime[1850:81640] name: devZhang