iOS项目中经常遇到数据的存储，NSArray、NSDictionary、NSString等等遵循了NSCopying协议的数据模型可以直接存储到本地，但是如果我是自定义的模型怎么办呢？

OC中有很多方式能够实现，但是今天我们说一个不需要借助于第三方的方式来实现：归档操作来存储。直接用归档方法，实现不了存储。这个时候我们可以通过遵守<NSCopying>协议来编码对象和解码对象操作

1、模型的 .h

#import <Foundation/Foundation.h>

@interface SmartCityModel : NSObject

@property (nonatomic, copy) NSString *cityName;         //名称 北京市

@property (nonatomic, copy) NSString *initial;          //首字母 bjs

@property (nonatomic, copy) NSString *citySpell;        //拼音 beijingshi

@property (nonatomic, copy) NSString *firstCharacter;   //b

@property (nonatomic, copy) NSString *secondCharacter;  //j

@property (nonatomic, copy) NSString *thirdCharacter;   //s

@end

2、模型的 .m

#import "SmartCityModel.h"

@implementation SmartCityModel

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.cityName forKey:@"cityName"];
    [aCoder encodeObject:self.initial forKey:@"initial"];
    [aCoder encodeObject:self.citySpell forKey:@"citySpell"];
    [aCoder encodeObject:self.firstCharacter forKey:@"firstCharacter"];
    [aCoder encodeObject:self.secondCharacter forKey:@"secondCharacter"];
    [aCoder encodeObject:self.thirdCharacter forKey:@"thirdCharacter"];
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super init]) {
        self.cityName = [aDecoder decodeObjectForKey:@"cityName"];
        self.initial = [aDecoder decodeObjectForKey:@"initial"];
        self.citySpell = [aDecoder decodeObjectForKey:@"citySpell"];
        self.firstCharacter = [aDecoder decodeObjectForKey:@"firstCharacter"];
        self.secondCharacter = [aDecoder decodeObjectForKey:@"secondCharacter"];
        self.thirdCharacter = [aDecoder decodeObjectForKey:@"thirdCharacter"];
    }
    return self;
}
@end

3、后面就可以直接使用这个模型(在这里我是把城市字符串转成城市模型)

//获取汉字转成拼音字符串  通讯录模糊搜索 支持拼音检索 首字母 全拼 汉字 搜索
+ (SmartCityModel *)transformToPinyin:(NSString *)aString
{
    SmartCityModel *model = [[SmartCityModel alloc] init];
    //转成了可变字符串
    NSMutableString *str = [NSMutableString stringWithString:aString];
    CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformMandarinLatin,NO);
    //再转换为不带声调的拼音
    CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformStripDiacritics,NO);
    NSArray *pinyinArray = [str componentsSeparatedByString:@" "];
    
    for (int i = 0; i < pinyinArray.count; i ++) {
        NSString *subString = pinyinArray[i];
        if (subString.length > 0) {
            subString = [subString substringToIndex:1];
            if (i == 0) {
                model.firstCharacter = subString;
            }else if (i == 1) {
                model.secondCharacter = subString;
            }else if (i == 2) {
                model.thirdCharacter = subString;
            }
        }
    }
    
    NSMutableString *initial = [NSMutableString string];
    for (NSString *s in pinyinArray){//首字母
        if (s.length > 0){
            [initial appendString:[s substringToIndex:1]];
        }
    }
    model.initial = initial;
    model.cityName = aString;

    NSMutableString *spell = [NSMutableString string];
    for (NSString *s in pinyinArray){//拼音
        [spell appendString:s];
    }
    model.citySpell = spell;
    
    return model;
}

4、缓存到本地时使用归档[NSKeyedArchiver archivedDataWithRootObject:];转成NSData来存储

+(void)cacheLocalRegion
{
    NSMutableArray *localRegionArray = @[].mutableCopy;
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    dispatch_async(queue, ^{
        NSData *regionData = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"region" ofType:@"json"]];
        NSError *error = nil;
        id reponse = [NSJSONSerialization JSONObjectWithData:regionData options:NSJSONReadingMutableContainers error:&error];
        if (!error) {
            if ([reponse isKindOfClass:[NSArray class]]) {
                NSArray *local = (NSArray *)reponse;
                NSMutableArray *localCityArray = @[].mutableCopy;
                for (NSDictionary *province in local) {
                    
                    NSString *provinceStr = province[@"name"];
                    if (![localCityArray containsObject:provinceStr]) {
                        [localCityArray addObject:provinceStr];
                    }
                    
                    NSArray *cityArray = province[@"city"];
                    for (NSDictionary *city in cityArray) {
                        
                        NSString *cityStr = city[@"name"];
                        if (![localCityArray containsObject:cityStr]) {
                            [localCityArray addObject:cityStr];
                        }
                        
                        NSArray *areaArray = city[@"area"];
                        for (NSString *areaStr in areaArray) {
                            if (![localCityArray containsObject:areaStr]) {
                                [localCityArray addObject:areaStr];
                            }
                        }
                    }
                }
                
                //转str --> 拼接字符串
                for (NSString *city in localCityArray) {
                    [localRegionArray addObject:[NSString transformToPinyin:city]];
                }
                
                //缓存在本地
                NSData *regionData = [NSKeyedArchiver archivedDataWithRootObject:localRegionArray];
                [[NSUserDefaults standardUserDefaults] setValue:regionData forKey:cacheRegion];
                [[NSUserDefaults standardUserDefaults] synchronize];
            }
        }else{
            [SmartToast Tost:@"地区解析失败"];
        }
    });
}

5、最后把NSData解档成存储时的数据就可以了

        NSData *regonData = [[NSUserDefaults standardUserDefaults] valueForKey:cacheRegion];
        NSArray *regionArray = [NSKeyedUnarchiver unarchiveObjectWithData:regonData];