数据持久化

    程序运行会分配一个沙盒文件,沙盒文件的文件名每次运行都会变化,文件夹名只一次有效,沙盒一般会保存程序一些信息,缓存等数据,还可以进行病毒的测试.    沙盒里有三个文件夹 Documents,libary,tmp.    Documents文件夹:保存用户想要保存的一些信息,比如收藏的内容,设置信息.    Library文件夹:用来保存开发人员存储的一些东西.    caches缓存文件夹:用来对缓存信息进行存储,清除缓存就是删除该文件夹.    Preferences用来保存一些信息,NSUserDefaults创建的plist文件保存在这个文件里.    tmp临时文件夹:存储临时文件.    NSBundle指的是当前工程的文件夹,在里面和可以获取图片等的信息,应用程序会在编译的时候把文件变成只读文件,存入到NSBundle里.

一.把简单的对象存入本地.// 简单对象指:NSString,NSArray....ViewController.m- (void)viewDidLoad {1.把字符串写入到本地.NSString *str = @"想象一下，在一个装满了平整细沙的盒子里，我们可以尽情随意地在上面作画、涂写，无论画的好坏，最后轻轻一抹，沙盒又回到了原来的平整状态.沙盒的魅力就在于他允许你出错，还可以给你改正的机会.";// ①.先找到目标文件夹的路径Documents// 参数1:前往指定文件夹的名,NSDocumentDirectory是documents用的,64行,注意不要和63行混用.还可以指定缓存等文件夹// 参数2:文件夹的类型,用户类型// 参数3:YES是绝对路径,能找到整个路径,NO是相对路径,只保留了前往的文件夹的名,前面用~代替.NSArray *sandBox = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);//    NSLog(@"%@", sandBox);// ②.寻找路径.NSString *sandBoxPath = sandBox[0];// 把要保存的内容进行路径的拼接NSString *docPath = [sandBoxPath stringByAppendingString:@"/老毛.plist"];// 把字符串写入到本地.// 参数1:写入的文件路径.// 参数2:是否保护正在写入的文件.// 参数3:编码格式.[str writeToFile:docPath atomically:YES encoding:NSUTF8StringEncoding error:nil];NSLog(@"%@", docPath);    // 从本地读字符串.    NSString *str = [NSString stringWithContentsOfFile:docPath encoding:NSUTF8StringEncoding error:nil];

2.把数组对象写入到本地.    NSArray *arr = @[@"小黑", @"小红", @"小白", @"小黄"];    NSArray *sandBox = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *sandBoxPath = sandBox[0];    // 路径拼接.    NSString *arrPath = [sandBoxPath stringByAppendingPathComponent:@"小韩.plist"];    // 按照指定的文件路径,数据写入到本地.    [arr writeToFile:arrPath atomically:YES];    NSLog(@"%@", arrPath);    // 从本地把数据读出来.    NSArray *receiveArr = [NSArray arrayWithContentsOfFile:arrPath];    for (NSString *str in receiveArr) {        NSLog(@"%@", str);    }     1.指定文件保存的沙盒文件路径.     2.拼接要保存的文件路径.     3.根据路径,把数据写入.     4.按照文件路径,从本地在读取数据.

3.把字典写入到本地.    NSDictionary *dic = @{@"1":@"2", @"3":@"4", @"5":@"6"};    NSArray *sandBox = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *sandBoxPath = sandBox[0];    NSString *dicPath = [sandBoxPath stringByAppendingPathComponent:@"kaka.MP4"];    [dic writeToFile:dicPath atomically:YES];    NSLog(@"%@", dicPath);    NSDictionary *receiveDic = [NSDictionary dictionaryWithContentsOfFile:dicPath];    NSLog(@"%@", receiveDic);    NSUserDefaults *user = [NSUserDefaults standardUserDefaults];    [user setObject:@"xiaohan" forKey:@"userName"];    NSLog(@"%@", NSHomeDirectory());}

Student.h#import <Foundation/Foundation.h>// 让复杂类写入到本地执行归档和反归档的操作,只有类签订NSCoding协议之后,实现协议方法才能进行归档和反归档的操作.@interface Student : NSObject<NSCopying>@property(nonatomic, copy)NSString *name;@property(nonatomic, copy)NSString *hobby;@property(nonatomic, assign)NSInteger age;@property(nonatomic, retain)NSNumber *number;- (instancetype)initWithName:(NSString *)name hobby:(NSString *)hobby         age:(NSInteger)age      number:(NSNumber *)number;@end

Student.m#import "Student.h"@implementation Student- (instancetype)initWithName:(NSString *)name hobby:(NSString *)hobby                         age:(NSInteger)age                      number:(NSNumber *)number {    self = [super init];    if (self) {        self.age = age;        self.name = name;        self.hobby = hobby;        self.number = number;    }    return self;}- (void)encodeWithCoder:(NSCoder *)aCoder {    // 对数据进行编码操作    // 把需要归档的数据进行编码操作.不需要的就不写了.    [aCoder encodeObject:self.name forKey:@"name"];    [aCoder encodeObject:self.hobby forKey:@"hobby"];    [aCoder encodeObject:self.number forKey:@"number"];    [aCoder encodeInteger:self.age forKey:@"age"];}- (id)initWithCoder:(NSCoder *)aDecoder {    self = [super init];    if (self) {        // 解码的操作        // 把解码之后的值在赋值给属性.        self.name = [aDecoder decodeObjectForKey:@"name"];        self.hobby = [aDecoder decodeObjectForKey:@"hobby"];        self.number = [aDecoder decodeObjectForKey:@"number"];        self.age = [aDecoder decodeIntegerForKey:@"age"];    }    return self;    }@end

4.把复杂对象,写入到本地.    Student *stu = [[Student alloc] init];    stu.name = @"小黑";    stu.hobby = @"小红";    stu.number = @100;    stu.age = 30;    // 归档操作.    // 找沙盒路径.    NSArray *sandBox = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *sandBoxPath = sandBox[0];    NSString *docPath = [sandBoxPath stringByAppendingPathComponent:@"小黄.MP4"];    NSLog(@"%@",docPath);    [NSKeyedArchiver archiveRootObject:stu toFile:docPath];    // 反归档.    Student *tempStu = [NSKeyedUnarchiver unarchiveObjectWithFile:docPath];    NSLog(@"%@, %@", tempStu.name, tempStu.hobby);//     把复杂对象放到数组里进行归档和反归档的操作    Student *stu1 = [[Student alloc] initWithName:@"小红" hobby:@"男" age:20 number:@100];    Student *stu2 = [[Student alloc] initWithName:@"小黄" hobby:@"女" age:21 number:@200];    Student *stu3 = [[Student alloc] initWithName:@"小白" hobby:@"女" age:22 number:@300];    Student *stu4 = [[Student alloc] initWithName:@"小黑" hobby:@"男" age:23 number:@400];    NSArray *arr = @[stu1, stu2, stu3, stu4];    for (Student *aaa in arr) {        NSLog(@"%@, %@, %ld, %@", aaa.name, aaa.hobby, aaa.age, aaa.number);    }    // 把复杂对象保存到数组中,然后整体进行归档和反归档的操作    // NSArray因为本身就签署了NSCoding协议,所以可以直接进行归档和反归档操作,自己写的复杂类也必须签NSCoding协议,实现方法,否则就会崩溃.

将plist文件,进行归档与反归档.    // 1.找路径    NSArray *sandBox1 = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *sandBoxPath1 = sandBox1[0];    // 2.拼接路径.    NSString *docPath1 = [sandBoxPath1 stringByAppendingPathComponent:@"student.plist"];    // 3.归档或者是写入.    [NSKeyedArchiver archiveRootObject:arr toFile:docPath1];    NSLog(@"%@", docPath1);    // 反归档.    NSArray *temp = [NSKeyedUnarchiver unarchiveObjectWithFile:docPath];    for (Student *stu in temp) {        NSLog(@"%@", stu.name);    }

5.文件管理    // 1.找到文件路径    NSArray *sandBox2 = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *sandBoxPath2 = sandBox2[0];    // 创建一个文件管理者.    NSFileManager *manager = [NSFileManager defaultManager];    // 要拼接一个文件夹的路径.    NSString *docPath2 = [sandBoxPath2 stringByAppendingPathComponent:@"ything"];    // 根据路径创建一个文件夹.    [manager createDirectoryAtPath:docPath2 withIntermediateDirectories:YES attributes:nil error:nil];    NSLog(@"********%@", docPath2);

6.删除文件夹,文件.    BOOL result = [manager removeItemAtPath:docPath2 error:nil];    if (result) {        NSLog(@"删除成功");    } else {        NSLog(@"删除失败");    }