关于数据持久化的一个简介

今天给大家介绍一个OC中的数据持久化,今天介绍其中的三种,plist存储,偏好设置存储及归档存储!下面分别给大家上代码,并在代码中进行详细注释!

一 plist存储(只能存储OC中这些如字典,数组等常见的数据类型,如果想存个自定义类型的数据是不支持的)

//存数据
- (void)saveArray
{
    // 1.获得沙盒根路径
    NSString *home = NSHomeDirectory();
    
    // 2.document路径
    NSString *docPath = [home stringByAppendingPathComponent:@"Documents"];
    
    // 3.新建数据
    NSArray *data = @[@"jack", @10, @"ffdsf"];
    
    
    NSString *filepath = [docPath stringByAppendingPathComponent:@"data.plist"];
    
    
    [data writeToFile:filepath atomically:YES];
}

//读取数据
- (IBAction)read {
    // 1.获得沙盒根路径
    NSString *home = NSHomeDirectory();
    
    // 2.document路径
    NSString *docPath = [home stringByAppendingPathComponent:@"Documents"];
    
    // 3.文件路径

    NSString *filepath = [docPath stringByAppendingPathComponent:@"data.plist"];
    
    // 4.读取数据
    NSArray *data = [NSArray arrayWithContentsOfFile:filepath];
    NSLog(@"%@", data);
}

二 偏好设置存储(故名思意,偏好设置存储就是存储我们APP的一些偏好设置,例如xcode中的preference)

- (IBAction)save {
    // 1.利用NSUserDefaults,就能直接访问软件的偏好设置(Library/Preferences)
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    
    // 2.存储数据
    [defaults setObject:@"mm" forKey:@"account"];
    [defaults setObject:@"123" forKey:@"pwd"];
    [defaults setInteger:10 forKey:@"age"];
    [defaults setBool:YES forKey:@"auto_login"];
    
    // 3.立刻同步
    [defaults synchronize];
}

- (IBAction)read {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    
    NSString *account = [defaults objectForKey:@"account"];
    BOOL autoLogin = [defaults boolForKey:@"auto_login"];
    NSLog(@"%@ -- %d", account, autoLogin);
}

三 归档

ViewController类

#import "ViewController.h"
#import "Student.h"

@interface ViewController ()
- (IBAction)save;
- (IBAction)read;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (IBAction)save {
    // 1.新的模型对象
    Student *stu = [[Student alloc] init];
    stu.no = @"42343254";
    stu.age = 20;
    stu.height = 1.55;
    
    // 2.归档模型对象
    // 2.1.获得Documents的全路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    // 2.2.获得文件的全路径
    NSString *path = [doc stringByAppendingPathComponent:@"stu.data"];
    // 2.3.将对象归档
    [NSKeyedArchiver archiveRootObject:stu toFile:path];
}

- (IBAction)read {
    // 1.获得Documents的全路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    // 2.获得文件的全路径
    NSString *path = [doc stringByAppendingPathComponent:@"stu.data"];
    
    // 3.从文件中读取MJStudent对象
    Student *stu = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    
    NSLog(@"%@ %d %f", stu.no, stu.age, stu.height);
}
@end

Student类

student.h(这里一定要遵守NSCoding协议,因为归档与反归档要利用NSCoding协议来对要存储的数据来进行编码 ,如果不遵守此协议便会报错!大家切记):

#import <Foundation/Foundation.h>

@interface Student : NSObject  <NSCoding>
@property (nonatomic, copy) NSString *no;
@property (nonatomic, assign) double height;
@property (nonatomic, assign) int age;
@end

student.m(这里要实现这两个方法,- (void)encodeWithCoder:(NSCoder *)encoder这个方法是对数据进行存储,并指定对哪几个数据进行存储;- (id)initWithCoder:(NSCoder *)decoder 显而易见这个方法肯定是要告诉我们读取哪些数据了!

#import "Student.h"

@interface Student() 

@end

@implementation Student

/**
 *  将某个对象写入文件时会调用
 *  在这个方法中说清楚哪些属性需要存储
 */
- (void)encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeObject:self.no forKey:@"no"];
    [encoder encodeInt:self.age forKey:@"age"];
    [encoder encodeDouble:self.height forKey:@"height"];
}

/**
 *  从文件中解析对象时会调用
 *  在这个方法中说清楚哪些属性需要存储
 */
- (id)initWithCoder:(NSCoder *)decoder
{
    if (self = [super init]) {
        // 读取文件的内容
        self.no = [decoder decodeObjectForKey:@"no"];
        self.age = [decoder decodeIntForKey:@"age"];
        self.height = [decoder decodeDoubleForKey:@"height"];
    }
    return self;
}
@end

到此为止如果有不明白的地方请给我留言,会详细解答.