四种保存数据的方法

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一、<span style="color:#ff0000;">NSKeyedArchiver</span>:采用归档的形式保存数据，该数据对象必须得遵守NSCoding协议，并且该对象对应的类必须提供encodeWithCoder：和initWithCoder方法，前<span style="white-space:pre"></span>   一个方法告诉系统怎么对对象进行编码，后一个对象则是告诉系统如何对队形进行解码：例子如下

首先是Person类

#import <UIKit/UIKit.h>@interface Person : UIView<NSCoding>@property (nonatomic,assign) int age;@property (nonatomic,copy)   NSString *name;@property (nonatomic,assign) float height;@end

#import "Person.h"@implementation Person#pragma mark 写入文件-(void)encodeWithCoder:(NSCoder *)aCoder{    [super encodeWithCoder:aCoder];//-----------不要忘记加这个    [aCoder encodeInt:self.age forKey:@"age"];    [aCoder encodeObject:self.name forKey:@"name"];    [aCoder encodeFloat:self.height forKey:@"height"];}#pragma mark 从文件中读取-(id)initWithCoder:(NSCoder *)aDecoder{    self = [super initWithCoder:aDecoder];//-----不要忘记加这个    self.age = [aDecoder decodeIntForKey:@"age"];    self.name = [aDecoder decodeObjectForKey:@"name"];    self.height = [aDecoder decodeFloatForKey:@"height"];    return self;}-(NSString *)description{    return [NSString stringWithFormat:@"name = %@,age = %d,height = %f",self.name,self.age,self.height];}@end

然后是ViewController

#import "ViewController.h"#import "Person.h"#define PERSON @"person1"@implementation ViewController-(void)viewDidLoad{    [super viewDidLoad];    [self createPerson];    [self readPerson];}-(void)createPerson{    Person *p = [[Person alloc]init];    p.age = 20;    p.name = @"Rio";    p.height = 1.75;        //获得Document路径    NSString *documents = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];    NSString *path = [documents stringByAppendingPathComponent:PERSON];        [NSKeyedArchiver archiveRootObject:p toFile:path];}-(void)readPerson{    NSString *documents = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];    NSString *path = [documents stringByAppendingPathComponent:PERSON];    Person *p = [NSKeyedUnarchiver unarchiveObjectWithFile:path];    NSLog(@"person:%@",p);}@end

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二、NSUserDefaults：用来保存应用程序设置和属性以及用户保存的数据，用户再次打开应用程序之后这些数据仍然存在。可以存储的类型包括：NSData、NSDate、NSString、NSNumber、NSArray、NSDictionary。如要存储其他类型数据，在需要转换为前面的类型，才能用NSUserDefaults存储，具体实现方法在下面

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