iOS：数据存储

一、Plist方式数据存取：

1.保存NSArray到document/plist中：

/*
保存NSArray到document/plist中
*/
- (void)saveNSArrayToPlist{
    //获取沙盒根路径
    NSString *home = NSHomeDirectory();
    //document路径
    NSString *docPath = [home stringByAppendingPathComponent:@"Documents"];
    //新建数据
    NSArray *data = @[@"姓名", @26, @"工程师"];
    NSString *filePath = [docPath stringByAppendingPathComponent:@"data.plist"];
    [data writeToFile:filePath atomically:YES];
}

2.从document/plist中读取NSArray数据：

/*
 从document/plist中读取NSArray数据
 */
- (void)readPlistConvertNSArray{
    //获取沙盒根路径
    NSString *home = NSHomeDirectory();
    //document路径
    NSString *docPath = [home stringByAppendingPathComponent:@"Documents"];
    //文件路径
    NSString *filePath = [docPath stringByAppendingPathComponent:@"data.plist"];
    //读取数据
    NSArray *data = [NSArray arrayWithContentsOfFile:filePath];
}

二、Preferences方式数据存取：

1.保存数据到Preferences(类试SharedPreference)：

/*
 保存数据到Preferences(类试SharedPreference)
 */
- (void)savePreferences{
    //获取NSUserDefaults对象
    NSUserDefaults *pref = [NSUserDefaults standardUserDefaults];
    //存储数据,key=value形式
    [pref setObject:@"值内容" forKey:@"key名称"];
    [pref setInteger:1 forKey:@"key名称"];
    [pref setBool:YES forKey:@"key名称"];
}

2.读取Preferences数据(类试SharedPreference)：

/*
 读取Preferences数据(类试SharedPreference)
 */
- (void)readPreferences{
    //获取NSUserDefaults对象
    NSUserDefaults *pref = [NSUserDefaults standardUserDefaults];
    NSString *value = [pref objectForKey:@"key名称"];
    BOOL isValue = [pref boolForKey:@"key名称"];
}

三、NSKeyedArchiver方式，单个对象到单个文件数据存取：

1.User.h文件中定义几个变量，实现NSCoding协议，代码：

#import <Foundation/Foundation.h>

@interface User : NSObject <NSCoding>

@property(nonatomic, copy) NSString *name;
@property(nonatomic, assign) NSInteger age;
@property(nonatomic, assign) BOOL isLogin;

@end

2.重写encodeWithCoder方法，保存各个属性值，重写initWithCoder方法，取出缓存中的值赋值给属性：

#import "User.h"

@implementation User

/*
 保存对象到缓存中时会调此方法
 */
- (void)encodeWithCoder:(NSCoder *)encoder{
    /*
     保存各个值
     */
    [encoder encodeObject:_name forKey:@"name"];
    [encoder encodeInteger:_age forKey:@"age"];
    [encoder encodeBool:_isLogin forKey:@"isLogin"];
}

/*
 读取缓存中的此对象时会调此方法
 */
- (id)initWithCoder:(NSCoder *)decoder{
    if(self = [super init]){
        /*
         获取各个存储的值，并赋值
         */
        _name = [decoder decodeObjectForKey:@"name"];
        _isLogin = [decoder decodeBoolForKey:@"isLogin"];
        _age = [decoder decodeIntegerForKey:@"age"];
    }
    return self;
}

@end

3.调用保存与读取方法：

/*
 保存对象
 */
- (void)saveObj{
    User *user = [[User alloc] init];
    user.name = @"姓名";
    user.age = 26;
    user.isLogin = YES;
    //获得Documents绝对路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //获取路径
    NSString *path = [doc stringByAppendingPathComponent:@"user.data"];
    //保存对象
    [NSKeyedArchiver archiveRootObject:user toFile:path];
}

/*
 读取对象
 */
- (void)readObj{
    //获得Documents绝对路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //获取路径
    NSString *path = [doc stringByAppendingPathComponent:@"user.data"];
    //读取对象
    User *user = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
}

四、NSKeyedArchiver方式，多个对象到同个文件的存取：

1.将多个对象存到同一个文件：

/*
 将多个对象存到同一个文件
 */
- (void)saveMultipleObj{
    //新建可变NSData
    NSMutableData *data = [NSMutableData data];
    NSKeyedArchiver *ka = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    User *user1 = nil;
    User *user2 = nil;
    //将多个对象存到NSMutableData
    [ka encodeObject:user1 forKey:@"key名称1"];
    [ka encodeObject:user2 forKey:@"key名称2"];
    
    //完成存储
    [ka finishEncoding];
    
    //获得Documents绝对路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //获取路径
    NSString *path = [doc stringByAppendingPathComponent:@"user.data"];
    
    //将NSMutableData中的数据存到文件
    [data writeToFile:path atomically:YES];
}

2.读取文件中的多个对象：

/*
 读到文件中的多个对象
 */
- (void)readMultipleObj{
    //获得Documents绝对路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //获取路径
    NSString *path = [doc stringByAppendingPathComponent:@"user.data"];

    //根据路径创建NSData
    NSData *data = [NSData dataWithContentsOfFile:path];
    //创建NSKeyedUnarchiver
    NSKeyedUnarchiver *ku = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
    
    //根据key获取对象
    User *user1 = [ku decodeObjectForKey:@"key名称1"];
    User *user2 = [ku decodeObjectForKey:@"key名称2"];
    
    //读取完成
    [ku finishDecoding];
}