NSUserdefaults的基本应用

简介

NSUserDefaults是一个单例，在整个程序中只有一个实例对象，他可以用于数据的永久保存，而且简单实用。适合存储轻量级的本地数据。

支持的数据类型：NSNumber（NSInteger、float、double），NSString，NSDate，NSArray，NSDictionary，BOOL

注意：对相同的Key赋值约等于一次覆盖，故要保证每一个Key的唯一性

存取简单数据到本地

• 取

    NSUserDefaults *userD = [NSUserDefaults standardUserDefaults];
    NSData *data = [userD objectForKey:@"UUID"];

• 存

[userD setObject:uuidString forKey:@"UUID"];
[userD synchronize];    //同步，确保保存成功

存取图片

• 存

    UIImage *img3;
    [[NSUserDefaults standardUserDefaults] setObject:UIImagePNGRepresentation(img3) forKey:@"sharePic3"];

    [[NSUserDefaults standardUserDefaults] synchronize];

• 取

    NSUserDefaults *userD = [NSUserDefaults standardUserDefaults];
    NSData* imageData = [userD objectForKey:@"sharePic1"];
    UIImage *img = [UIImage imageWithData:imageData];

存取字典

存取的字典对象都必须是不可变的
-存

    // 新增的字典
    NSDictionary *dicAdd = @{@"key" : @"value"};
    // 添加
    [cur_dict addEntriesFromDictionary:dicAdd];
    // 先化为不可变字典，再保存
    NSDictionary *fdict =[[NSDictionary alloc] initWithDictionary:cur_dict]; 
   [[NSUserDefaults standardUserDefaults] setObject:fdict forKey:@"Adict"];

-取

    // 取出
    NSDictionary *dict = [[NSUserDefaults standardUserDefaults] dictionaryForKey:@"Adict"];
    // 化为可变字典 进行后续操作
    NSMutableDictionary *cur_dict = [[NSMutableDictionary alloc] initWithCapacity:0];
    [cur_dict addEntriesFromDictionary:dict];

存取数组

存取的数组对象都必须是不可变的

• 存

    NSMutableArray *mutableArray = [NSMutableArray arrayWithObjects:@"123",@"234", nil];
    //  先转换为不可变 数组
    NSArray * array = [NSArray arrayWithArray:mutableArray];
    
    NSUserDefaults *user = [NSUserDefaults standardUserDefaults];
    [user setObject:array forKey:@"names"];

• 取

    NSUserDefaults *userD = [NSUserDefaults standardUserDefaults];
    
    NSArray *arr = [userD arrayForKey:@"names"];

    NSMutableArray *mutableArray = [NSMutableArray arrayWithArray:arr];

应用：存储自定义对象

创建一个模型（user）

在.h中

#import <Foundation/Foundation.h>

@interface PDUser : NSObject<NSCoding>

@property(nonatomic,strong)NSString *apiKey;
@property(nonatomic,strong)NSString *apiSecret;
@property(nonatomic,strong)NSString *regDev;

@property(nonatomic,assign)NSInteger user_id;

@end

在.m中

#import "PDUser.h"

@implementation PDUser

-(void)encodeWithCoder:(NSCoder *)aCoder{
    
    
    [aCoder encodeObject:self.apiKey forKey:@"apiKey"];
    [aCoder encodeObject:self.apiSecret forKey:@"apiSecret"];
    [aCoder encodeObject:self.regDev forKey:@"UUID"];
    [aCoder encodeObject:[NSString stringWithFormat:@"%ld",self.user_id] forKey:@"userid"];

}

-(instancetype)initWithCoder:(NSCoder *)aDecoder{
    
    if(self = [super init]){
        
        self.apiKey = [aDecoder decodeObjectForKey:@"apiKey"];
        self.apiSecret = [aDecoder decodeObjectForKey:@"apiSecret"];
        self.regDev = [aDecoder decodeObjectForKey:@"UUID"];
        self.user_id = [[aDecoder decodeObjectForKey:@"userid"] integerValue];
    
    }
    return self;
}

外界使用

保存在userdefault中，以及从中取出user

• 保存

//把user对象存入 userdefault
        NSUserDefaults *userD = [NSUserDefaults standardUserDefaults];
        
        PDUser *user = [[PDUser alloc] init];
        user.apiSecret = _reBackData.apiSecret;
        user.apiKey = _reBackData.apiKey;
        user.regDev = _reBackData.regDev;
        user.user_id = _reBackData.user_id;
        
        NSData *data = [NSKeyedArchiver archivedDataWithRootObject:user];
        [userD setObject:data forKey:@"USER"];     //保存

• 取出

//从中取出user对象
        NSUserDefaults *userD = [NSUserDefaults standardUserDefaults];
        NSData *data = [userD objectForKey:@"USER"];
        PDUser *user = [NSKeyedUnarchiver unarchiveObjectWithData:data];