iOS的APP可以在自己的沙盒里读写文件，但是不可以访问其他APP的沙盒。每一个APP都是一个信息孤立的房间，这些房间就相当于一个沙盒，相互是不可以进行通信的，唯独可以通过URL Scheme。沙盒里面的文件可以是照片、声音文件、文件、属性列表等。

沙盒的根目录结构:Document、Library、temp。
1.Document：用于存储用户数据，iTunes备份和恢复的时候会包括此目录。所以。苹果建议将程序中建立的或在程序中浏览到的文件数据保存在该目录下。
2.Library：包含两个子目录：Caches 和 Preferences。Caches用来存放用户需要换成的文件。Preferences是APP的偏好设置，可以通过NSUserDefaults来读取和设置。
3.tmp：用于存放临时文件，这个可以存放一些当APP退出后不需要再保存的文件。

获取沙盒路径

 //获取路径三种方法
 NSString *path = NSHomeDirectory();
 //拼接字符串
 NSString *documents = [path stringByAppendingString:@"/Documents"];
 //专业拼接路径
 NSString *str = [path stringByAppendingPathComponent:@"Documents"];

系统提供的方法获取Document路径

NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *strD = [array objectAtIndex:0];
NSLog(@"%@",strD);

获取library路径

NSArray *arrayL = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *strL = [arrayL objectAtIndex:0];
NSLog(@"%@",strL);

获取tmp路径

NSString *path = NSTemporaryDirectory();
NSLog(@"%@",path);

获取caches路径

NSArray *arrayC = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *strC = [arrayC objectAtIndex:0];
NSLog(@"%@",strC);

用NSUserDefaults对Preferences进行读取和设置

NSUserDefaults *user = [NSUserDefaults standardUserDefaults];
[user setObject:@"zhangsan" forKey:@"name"];
[user setObject:@"lisi" forKey:@"names"];
//将数据同步到沙盒的规定目录下（library下的preferences目录）
[user synchronize];

基本类型数据的存储和读取

• 字符串存储、读取

- (void)saveString{
    //获取Document目录
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //在沙盒文件下创建文件
    NSString *newPath = [string stringByAppendingString:@"/text.txt"];
    //要存入的内容
    NSString *name = @"UMR";
    //写入文件
    [name writeToFile:newPath atomically:YES encoding:NSUTF8StringEncoding error:nil];
}
- (void)readingString{
    //获取路径
    NSString *str = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [str stringByAppendingString:@"/text.txt"];
    //读取数据
    NSString *string = [NSString stringWithContentsOfFile:newPath encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"%@",string);
}

• 数组存储、读取

- (void)saveArray{
    //1.获取路径
    //获取目录
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //在沙盒文件下创建文件
    NSString *newPath = [string stringByAppendingString:@"/array.plist"];
    //要存入的内容
    NSArray *array = @[@"zhangsan",@"lisi",@"wangwu"];
    //写入
    [array writeToFile:newPath atomically:YES];
    NSLog(@"%@",newPath);
}
- (void)readingArray{
    //获取路径
    NSString *str = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [str stringByAppendingString:@"/array.plist"];
    //读取数据
    NSArray *array = [NSArray arrayWithContentsOfFile:newPath];
    NSLog(@"%@",array);
}

• 字典存储、读取

- (void)saveDictionary{
    //获取路径
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [string stringByAppendingString:@"/dictionary.plist"];
    //存储内容
    NSDictionary *dict = @{@"n1":@[@"1",@"2",@"3"],@"n2":@{@"a":@"d",@"s":@"g"},@"n3":@"uuummmrrr"};
    [dict writeToFile:newPath atomically:YES];
    NSLog(@"%@",newPath);
}
- (void)readingDictionary{
    //获取路径
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [string stringByAppendingString:@"/dictionary.plist"];
    //读取内容
    NSDictionary *dic = [NSDictionary dictionaryWithContentsOfFile:newPath];
    NSLog(@"%@",dic);
}

• data存储、读取

- (void)saveData{
    //获取路径
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //存储路径
    NSString *newPath = [string stringByAppendingString:@"/data.plist"];
    //存储内容
    NSString *str = @"UMR";
    //将string转换成data
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    //写入文件夹
    [data writeToFile:newPath atomically:YES];
    NSLog(@"%@",newPath);
}
- (void)readingData{
    //获取路径
    NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //存储路径
    NSString *newPath = [string stringByAppendingString:@"/data.plist"];
    //从文件读取data
    NSData *data = [NSData dataWithContentsOfFile:newPath];
    //将data转换成为string
    NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"%@",str);
}

• image存储 - 需转换为data进行存储和读取

- (void)saveImage{
    //获取路径
    NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    //在文件路径下面创建该文件夹
    NSString *newPath = [path stringByAppendingString:@"/image.png"];
    //将.png转为data格式
    NSData *imageData = UIImagePNGRepresentation([UIImage imageNamed:@"name6.png"]);
//    NSData *imageD = UIImageJPEGRepresentation([UIImage imageNamed:@"name6.png"], 1); 如果是JPG格式的，后面的CGFloat为压缩系数;
    //将data文件写入文件夹
    [imageData writeToFile:newPath atomically:YES];
    NSLog(@"%@",newPath);
}
- (void)readingImage{
    //获取路径，获取文件
    NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [path stringByAppendingString:@"/image.png"];
    NSData *imageData = [NSData dataWithContentsOfFile:newPath];
    //将data转为图片格式
    UIImage *image = [UIImage imageWithData:imageData];
    //获取 - 赋值
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(120, 120, 120, 120)];
    imageView.image = image;
    [self.view addSubview:imageView];
    NSLog(@"%@",newPath);
}

归档与反归档 - 复杂数据的沙盒存储

• eg：先创建一个Person对象，声明相关属性

//归档必须遵守NSCoding协议
@interface Person : NSObject<NSCoding>
@property (nonatomic,strong) NSString *name;
@property (nonatomic,strong) NSString *gender;
@property (nonatomic,assign) NSInteger age;
@end```
 - 在.m文件中实现这两个NSCoding协议方法

@implementation Person
//对对象进行归档的时候调用

• (void)encodeWithCoder:(NSCoder *)aCoder{
  [aCoder encodeObject:self.name forKey:@"name"];
  [aCoder encodeObject:self.gender forKey:@"gender"];
  [aCoder encodeInteger:self.age forKey:@"age"];
  }
  //对对象进行反归档的时候调用
• (instancetype)initWithCoder:(NSCoder *)aDecoder{
  if (self = [super init]) {
  self.name = [aDecoder decodeObjectForKey:@"name"];
  self.gender = [aDecoder decodeObjectForKey:@"gender"];
  self.age = [aDecoder decodeIntegerForKey:@"age"];
  }
  return self;
  }
  @end```
• 归档

- (void)saveData{
    Person *person = [[Person alloc] init];
    person.name = @"umr";
    person.gender = @"m";
    person.age = 18;
    //进行规档操作
    //1.创建一个NSMutableData来存储归档后的数据
    NSMutableData *Data = [[NSMutableData alloc] init];
    //2.创建归档器
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:Data];
    //3.进行归档
    [archiver encodeObject:person forKey:@"person"];
    //4.归档结束
    [archiver finishEncoding];
    //获取沙盒路径
    NSString *SDPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *newPath = [SDPath stringByAppendingString:@"/archiver.plist"];
    //写入文件
    [Data writeToFile:newPath atomically:YES];
    NSLog(@"%@",newPath);
}```
 - 反归档

• (void)readData{
  //获取沙盒路径
  NSString *path = [[self documentPath] stringByAppendingString:@"/archiver.plist"];
  //获取数据
  NSData *data = [NSData dataWithContentsOfFile:path];
  NSKeyedUnarchiver *Unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
  Person *person1 = [Unarchiver decodeObjectForKey:@"person"];
  [Unarchiver finishDecoding];
  NSLog(@"%@ %ld %@",person1.name,person1.age,person1.gender);
  }```

- (NSString *)documentPath{
    return [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
}```
### - 对象数组的归档与反归档

• (void)codeArray{
  //创建两个person对象
  Person *person1 = [[Person alloc] init];
  person1.name = @"huahua";
  Person *person2 = [[Person alloc] init];
  person2.name = @"UMR";

  存入数组 - 数组中的复杂对象必须遵守NSCoding协议，就可以直接对数组进行归档

  NSMutableArray *array = [[NSMutableArray alloc] initWithObjects:person1,person2, nil];
  //获取路径
  NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
  NSString *path = [documentPath stringByAppendingPathComponent:@"array.plist"];
  NSLog(@"%@",path);
  //归档
  [NSKeyedArchiver archiveRootObject:array toFile:path];
  //反归档
  NSArray *arr = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
  // Person *per = arr[0];
  NSLog(@"%@",arr);
  }```