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[操作系统]ios缓存系列



     1. 程序中什么时候用到缓存

 

  2. 缓存机制

    1)第一次请求数据时,内存缓存中没有数据,硬盘缓存中没有数据。

      

    2)当服务器返回数据时,需要做一下步骤

              1>使用服务器的数据

              2>将服务器的数据缓存到硬盘(沙盒)

    此时,内存缓存中有数据,硬盘缓存中没有数据

     

    3)再次请求数据分为两种情况:

              1>如果程序并没有关闭,一直在运行,

              那么此时内存缓存中有数据,硬盘缓存中有数据。如果此时再次请求数据,直接使用内存缓存中的数据即可。

              2>如果程序重新启动

              那么此时内存缓存的数据已经消失,硬盘缓存依旧存在,如果此时再请求数据,直接使用硬盘缓存的数据即可。

    提示:从硬盘缓存中读取数据后,内存缓存中又有数据了。

  3.缓存的几种常用方法及具体如何使用

    1) 归档  

    2) 生成plist 

    3) NSUserDefault

    4) sqlite

 

1.1>归档:可以存放自定义对象  <NSCoding>

常用方法:  //存    [NSKeyedArchiver archiveRootObject:p toFile:path];

       //取  [NSKeyedUnarchiver unarchiverObjectWithFile:path];

       /*当将一个自定义对象保存到文件的时候就会调用该方法,在该方法中说明如何存储自定义对象的属性*/

      -(void)encodeWithCoder:(NSCoder *)aCoder

      /*当文件中读取一个对象的时候回调用该方法,在该方法中说明如何读取保存在文件中的对象*/

      -(id)initWithCoder:(NSCoder *)aDecoder

1 #import <Foundation/Foundation.h>2 3 @interface Person : NSObject<NSCoding>4 5 @property (nonatomic, copy) NSString *name;6 @property (nonatomic, assign) NSInteger age;7 @property (nonatomic, assign) BOOL sex;8 9 @end

#import "Person.h"@implementation Person//归档- (void)encodeWithCoder:(NSCoder *)aCoder{  [aCoder encodeObject:self.name forKey:@"name"];  [aCoder encodeInteger:self.age forKey:@"age"];  [aCoder encodeBool:self.sex forKey:@"sex"];}//解档- (instancetype)initWithCoder:(NSCoder *)aDecoder{  if (self == [super init]) {    self.name = [aDecoder decodeObjectForKey:@"name"];    self.age = [aDecoder decodeIntegerForKey:@"age"];    self.sex = [aDecoder decodeBoolForKey:@"sex"];  }  return self;}@end

#import "ViewController.h"#import "Person.h"@interface ViewController ()@property (nonatomic, strong) Person *person;@end@implementation ViewController- (void)viewDidLoad {  [super viewDidLoad];    [self saveCacheData];}- (Person *)person{  if (_person == nil) {    _person = [[Person alloc] init];    _person.name = @"xinjinying";    _person.age = 11;    _person.sex = YES;  }  return _person;}#pragma mark - 归档存储缓存数据- (void)saveCacheData{  NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];  NSString *cachePath = [path stringByAppendingPathComponent:@"tooyoung.toosimple"];  NSLog(@"%@",cachePath);  [NSKeyedArchiver archiveRootObject:self.person toFile:cachePath];}- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{  NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];  NSString *readDataPath = [path stringByAppendingPathComponent:@"tooyoung.toosimple"];  NSLog(@"%@",readDataPath);  Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:readDataPath];  NSLog(@"%@-%zd-%d",person.name,person.age,person.sex); }

2.1>生成plist文件

#pragma mark - 写入读取plist文件- (void)writeAndReadPlistFile{  //读取plist  NSString *plistPath = [[NSBundle mainBundle] pathForResource:@"plistdemo" ofType:@"plist"];  NSMutableDictionary *data = [[NSMutableDictionary alloc] initWithContentsOfFile:plistPath];    //添加一项内容  [data setObject:@"yoyoyo" forKey:@"key"];    //存入yoyoyo.plist  NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];  NSString *writePath = [path stringByAppendingPathComponent:@"yoyoyo.plist"];  [data writeToFile:writePath atomically:YES];  }

3.1>NSUserDefault(项目里一般用来存用户名,密码,accessToken,版本号...)

 1 #pragma mark - NSUserdefaults 2 - (void)userDefaultCache 3 { 4   //存   5   NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults]; 6   [userDefaults setObject:@"fuck" forKey:@"name"]; 7   [userDefaults synchronize]; 8 } 9 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event10 {11   //取12   NSUserDefaults *userDetaults = [NSUserDefaults standardUserDefaults];13   NSString *name = [userDetaults objectForKey:@"name"];14   NSLog(@"%@",name);15 }  

 

待续...