ios应用数据存储方式(归档)

一.简单说明 
　　1.在使用plist进行数据存储和读取，只适用于系统自带的一些常用类型才能用，且必须先获取路径相对麻烦。 
　　2.偏好设置(将所有的东西都保存在同一个文件夹下面，且主要用于存储应用的设置信息)。 
　　3.归档:因为前两者都有一个致命的缺陷，只能存储常用的类型。归档可以实现把自定义的对象存储放在文件中。

1.代码示例   DBPerson.h文件

//如果想将一个自定义对象保存到文件中必须实现NSCoding协议
@interface DBPerson : NSObject <NSCoding>
//姓名
@property(nonatomic,copy) NSString *name;
//年龄
@property(nonatomic,assign) int age;
//身高
@property(nonatomic,assign) double height;
@end

DBPerson.m文件

#import "DBPerson.h"
@implementation DBPerson
/**
 *  1.当将一个自定义对象保存到文件的时候就会调用该方法
 *  2.在该方法中说明如何存储自定义对象的属性
 *  3.也就说在该方法中说清楚存储自定义对象的哪些属性
 */
- (void)encodeWithCoder:(NSCoder *)aCoder{
    NSLog(@"调用了encodeWithCoder:方法");
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeInteger:self.age forKey:@"age"];
    [aCoder encodeDouble:self.height forKey:@"height"];
}

/**
 *  1.当从文件中读取一个对象的时候就会调用该方法
 *  2.在该方法中说明如何读取保存在文件中的对象
 *  3.也就是说在该方法中说清楚怎么读取文件中的对象
 */
- (id)initWithCoder:(NSCoder *)aDecoder{
    NSLog(@"调用了initWithCoder:方法");
    if (self = [super init]) {
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.age = (int)[aDecoder decodeIntegerForKey:@"age"];
        self.height = [aDecoder decodeDoubleForKey:@"height"];
    }
    return self;
}
@end

ViewController.m文件

#import "ViewController.h"
#import "DBPerson.h"

#define CURRENT_SCREEN_WIDTH     [UIScreen mainScreen].bounds.size.width
#define CURRENT_SCREEN_HEIGHT     ([UIScreen mainScreen].bounds.size.height - 64)
#define BUTTON_WIDTH     80
#define BUTTON_HEIGHT    40

@interface ViewController ()
//保存数据按钮
@property(nonatomic,strong) UIButton *saveButton;
//读取数据按钮
@property(nonatomic,strong) UIButton *readButton;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self initControl];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

//初始化控件
- (void)initControl{
    _saveButton = [[UIButton alloc] initWithFrame:CGRectMake(CURRENT_SCREEN_WIDTH/2 - BUTTON_WIDTH/2,
                                                             CURRENT_SCREEN_HEIGHT/2 - BUTTON_HEIGHT,
                                                             BUTTON_WIDTH,
                                                             BUTTON_HEIGHT)];
    [_saveButton setTitle:@"保存数据" forState:UIControlStateNormal];
    [_saveButton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [_saveButton addTarget:self
                    action:@selector(saveClick)
          forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_saveButton];

    _readButton = [[UIButton alloc] initWithFrame:CGRectMake(CURRENT_SCREEN_WIDTH/2 - BUTTON_WIDTH/2,
                                                             _saveButton.frame.origin.y + _saveButton.frame.size.height + 60,
                                                             BUTTON_WIDTH,
                                                             BUTTON_HEIGHT)];
    [_readButton setTitle:@"读取数据" forState:UIControlStateNormal];
    [_readButton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [_readButton addTarget:self
                    action:@selector(readClick)
          forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_readButton];

}

#pragma mark -按钮事件
- (void)saveClick{
    //创建对象
    DBPerson *person = [[DBPerson alloc] init];
    person.name = @"文丁丁";
    person.age = 31;
    person.height = 1.76f;

    //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];
    NSLog(@"path = %@",path);

    //将自定义的对象保存到文件中
    [NSKeyedArchiver archiveRootObject:person
                                toFile:path];
}

- (void)readClick{
    //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];

    //从文件中读取对象
    DBPerson *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"name = %@",person.name);
    NSLog(@"age = %d",person.age);
    NSLog(@"height = %f",person.height);
}
@end

三.继承类中的使用 
DBStudent.h文件

#import "DBPerson.h"
@interface DBStudent : DBPerson
//增加一个体重属性
@property(nonatomic,assign) double weight;
@end

DBStudent.m文件

#import "DBStudent.h"
@implementation DBStudent
//在子类中重写这两个方法
- (void)encodeWithCoder:(NSCoder *)aCoder{
    [super encodeWithCoder:aCoder];
    NSLog(@"调用了DBStudent encodeWithCoder");
    [aCoder encodeFloat:self.weight forKey:@"weight"];
}

- (id)initWithCoder:(NSCoder *)aDecoder{
    if (self = [super initWithCoder:aDecoder]) {
        NSLog(@"调用了DBStudent initWithCoder");
        self.weight = [aDecoder decodeFloatForKey:@"weight"];
    }
    return self;
}
@end

ViewController.m文件

#import "ViewController.h"
#import "DBStudent.h"

#define CURRENT_SCREEN_WIDTH     [UIScreen mainScreen].bounds.size.width
#define CURRENT_SCREEN_HEIGHT     ([UIScreen mainScreen].bounds.size.height - 64)
#define BUTTON_WIDTH     80
#define BUTTON_HEIGHT    40

@interface ViewController ()
//保存数据按钮
@property(nonatomic,strong) UIButton *saveButton;
//读取数据按钮
@property(nonatomic,strong) UIButton *readButton;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self initControl];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

//初始化控件
- (void)initControl{
    _saveButton = [[UIButton alloc] initWithFrame:CGRectMake(CURRENT_SCREEN_WIDTH/2 - BUTTON_WIDTH/2,
                                                             CURRENT_SCREEN_HEIGHT/2 - BUTTON_HEIGHT,
                                                             BUTTON_WIDTH,
                                                             BUTTON_HEIGHT)];
    [_saveButton setTitle:@"保存数据" forState:UIControlStateNormal];
    [_saveButton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [_saveButton addTarget:self
                    action:@selector(saveClick)
          forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_saveButton];

    _readButton = [[UIButton alloc] initWithFrame:CGRectMake(CURRENT_SCREEN_WIDTH/2 - BUTTON_WIDTH/2,
                                                             _saveButton.frame.origin.y + _saveButton.frame.size.height + 60,
                                                             BUTTON_WIDTH,
                                                             BUTTON_HEIGHT)];
    [_readButton setTitle:@"读取数据" forState:UIControlStateNormal];
    [_readButton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    [_readButton addTarget:self
                    action:@selector(readClick)
          forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_readButton];

}

#pragma mark -按钮事件
- (void)saveClick{
//    //创建对象
//    DBPerson *person = [[DBPerson alloc] init];
//    person.name = @"文丁丁";
//    person.age = 31;
//    person.height = 1.76f;

    DBStudent *student = [[DBStudent alloc] init];
    student.name = @"wendingding";
    student.age = 31;
    student.height = 1.80f;
    student.weight = 100;

    //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];
    NSLog(@"path = %@",path);

    //将自定义的对象保存到文件中
    [NSKeyedArchiver archiveRootObject:student
                                toFile:path];
}

- (void)readClick{
    //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];

    //从文件中读取对象
    DBStudent *student = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"name = %@",student.name);
    NSLog(@"age = %d",student.age);
    NSLog(@"height = %f",student.height);
    NSLog(@"weight = %f",student.weight);
}
@end

四.重要说明 
1.保存数据过程

//    //创建对象
//    DBPerson *person = [[DBPerson alloc] init];
//    person.name = @"文丁丁";
//    person.age = 31;
//    person.height = 1.76f;

    DBStudent *student = [[DBStudent alloc] init];
    student.name = @"wendingding";
    student.age = 31;
    student.height = 1.80f;
    student.weight = 100;

    //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];
    NSLog(@"path = %@",path);

    //将自定义的对象保存到文件中
    [NSKeyedArchiver archiveRootObject:student
                                toFile:path];

2.读取数据过程

 //获取文件路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [docPath stringByAppendingPathComponent:@"person.yangyang"];

    //从文件中读取对象
    DBStudent *student = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"name = %@",student.name);
    NSLog(@"age = %d",student.age);
    NSLog(@"height = %f",student.height);
    NSLog(@"weight = %f",student.weight);

3.遵守 NSCoding 协议，并实现该协议中的两个方法。

4.如果是继承，则子类一定要重写那两个方法。因为person的子类在存取的时候，会去子类中去找调用的方法，没找到那么它就去父类中找，所以最好保存和读取的时候新增加的属性会被忽略。需要先调用父类的方法，先初始化父类的，在初始化子类的。

5.保存数据的文件的后缀名可以随意命名。

6.通过plist保存的数据是直接显示的，不安全。通过归档方法的数据在文件中打开是乱码的，更安全。