1.應(yīng)用沙盒
每個(gè)iOS應(yīng)用都有自己的應(yīng)用沙盒(應(yīng)用沙盒就是文件系統(tǒng)目錄)，與其他文件系統(tǒng)隔離。應(yīng)用必須待在自己的沙盒里，其他應(yīng)用不能訪問該沙盒。

Documents：保存應(yīng)用運(yùn)行時(shí)生成的需要持久化的數(shù)據(jù)，iTunes同步設(shè)備時(shí)會(huì)備份該目錄。例如，游戲應(yīng)用可將游戲存檔保存在該目錄

tmp：保存應(yīng)用運(yùn)行時(shí)所需的臨時(shí)數(shù)據(jù)，使用完畢后再將相應(yīng)的文件從該目錄刪除。應(yīng)用沒有運(yùn)行時(shí)，系統(tǒng)也可能會(huì)清除該目錄下的文件。iTunes同步設(shè)備時(shí)不會(huì)備份該目錄

Library/Caches：保存應(yīng)用運(yùn)行時(shí)生成的需要持久化的數(shù)據(jù)，iTunes同步設(shè)備時(shí)不會(huì)備份該目錄。一般存儲(chǔ)體積大、不需要備份的非重要數(shù)據(jù)

Library/Preference：保存應(yīng)用的所有偏好設(shè)置，iOS的Settings(設(shè)置)應(yīng)用會(huì)在該目錄中查找應(yīng)用的設(shè)置信息。iTunes同步設(shè)備時(shí)會(huì)備份該目錄

利用NSSearchPathForDirectoriesInDomains函數(shù)獲取應(yīng)用沙盒目錄
tmp路徑

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

documents路徑

//NSUserDomainMask 代表從用戶文件夾下找
// 是否展開全路徑
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
 // 在iOS中,只有一個(gè)目錄跟傳入的參數(shù)匹配,所以這個(gè)集合里面只有一個(gè)元素:
NSString *documentsPath = [array objectAtIndex:0];
NSLog(@"%@",documentsPath);

Preferences路徑

NSString *preferenceParh = NSSearchPathForDirectoriesInDomains(NSPreferencePanesDirectory, NSUserDomainMask, YES)[0];
NSLog(@"preferencePath:%@",preferenceParh);

Caches路徑

NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];NSLog(@"cache:%@",cachePath);

2.屬性列表
屬性列表是一種XML格式的文件，拓展名為plist
如果對(duì)象是NSString、NSDictionary、NSArray、NSData、NSNumber等類型，就可以使用writeToFile:atomically:方法直接將對(duì)象寫到屬性列表文件中
將一個(gè)NSDictionary對(duì)象歸檔到一個(gè)plist屬性列表中

// 將數(shù)據(jù)封裝成字典
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"母雞" forKey:@"name"];
[dict setObject:@"15013141314" forKey:@"phone"];
[dict setObject:@"27" forKey:@"age"];
// 將字典持久化到Documents/stu.plist文件中
[dict writeToFile:path atomically:YES];

讀取屬性列表，恢復(fù)NSDictionary對(duì)象

// 讀取Documents/stu.plist的內(nèi)容，實(shí)例化NSDictionary
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path];
NSLog(@"name:%@", [dict objectForKey:@"name"]);
NSLog(@"phone:%@", [dict objectForKey:@"phone"]);
NSLog(@"age:%@", [dict objectForKey:@"age"]);

3.偏好設(shè)置
保存數(shù)據(jù)

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"itcast" forKey:@"username"];
[defaults setFloat:18.0f forKey:@"text_size"];
[defaults setBool:YES forKey:@"auto_login"];
[defaults synchornize];

讀取上次保存的設(shè)置

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *username = [defaults stringForKey:@"username"];
float textSize = [defaults floatForKey:@"text_size"];
BOOL autoLogin = [defaults boolForKey:@"auto_login"];

4.NSKeyedArchiver
如果對(duì)象是NSString、NSDictionary、NSArray、NSData、NSNumber等類型，可以直接用NSKeyedArchiver進(jìn)行歸檔和恢復(fù)
不是所有的對(duì)象都可以直接用這種方法進(jìn)行歸檔，只有遵守了NSCoding協(xié)議的對(duì)象才可以
NSCoding協(xié)議有2個(gè)方法：

encodeWithCoder:
每次歸檔對(duì)象時(shí)，都會(huì)調(diào)用這個(gè)方法。一般在這個(gè)方法里面指定如何歸檔對(duì)象中的每個(gè)實(shí)例變量，可以使用encodeObject:forKey:方法歸檔實(shí)例變量
initWithCoder:
每次從文件中恢復(fù)(解碼)對(duì)象時(shí)，都會(huì)調(diào)用這個(gè)方法。一般在這個(gè)方法里面指定如何解碼文件中的數(shù)據(jù)為對(duì)象的實(shí)例變量，可以使用decodeObject:forKey方法解碼實(shí)例變量

歸檔一個(gè)NSArray對(duì)象到Documents/array.archive

NSArray *array = [NSArray arrayWithObjects:@”a”,@”b”,nil];
[NSKeyedArchiver archiveRootObject:array toFile:path];

恢復(fù)(解碼)NSArray對(duì)象

NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

歸檔Person對(duì)象

@interface Person : NSObject<NSCoding>
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, assign) float height;
@end

@implementation Person
- (void)encodeWithCoder:(NSCoder *)encoder {
    [encoder encodeObject:self.name forKey:@"name"];
    [encoder encodeInt:self.age forKey:@"age"];
    [encoder encodeFloat:self.height forKey:@"height"];
}
- (id)initWithCoder:(NSCoder *)decoder {
    self.name = [decoder decodeObjectForKey:@"name"];
    self.age = [decoder decodeIntForKey:@"age"];
    self.height = [decoder decodeFloatForKey:@"height"];
    return self;
}

@end

歸檔(編碼)
Person *person = [[[Person alloc] init] autorelease];
person.name = @"MJ";
person.age = 27;
person.height = 1.83f;
[NSKeyedArchiver archiveRootObject:person toFile:path];
恢復(fù)(解碼)
Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

注意事項(xiàng)

如果父類也遵守了NSCoding協(xié)議，請(qǐng)注意：
應(yīng)該在encodeWithCoder:方法中加上一句
[super encodeWithCode:encode];
確保繼承的實(shí)例變量也能被編碼，即也能被歸檔
應(yīng)該在initWithCoder:方法中加上一句
self = [super initWithCoder:decoder];
確保繼承的實(shí)例變量也能被解碼，即也能被恢復(fù)

使用archiveRootObject:toFile:方法可以將一個(gè)對(duì)象直接寫入到一個(gè)文件中，但有時(shí)候可能想將多個(gè)對(duì)象寫入到同一個(gè)文件中，那么就要使用NSData來進(jìn)行歸檔對(duì)象

歸檔（編碼）
// 新建一塊可變數(shù)據(jù)區(qū)
NSMutableData *data = [NSMutableData data];
// 將數(shù)據(jù)區(qū)連接到一個(gè)NSKeyedArchiver對(duì)象
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
// 開始存檔對(duì)象，存檔的數(shù)據(jù)都會(huì)存儲(chǔ)到NSMutableData中
[archiver encodeObject:person1 forKey:@"person1"];
[archiver encodeObject:person2 forKey:@"person2"];
// 存檔完畢(一定要調(diào)用這個(gè)方法)
[archiver finishEncoding];
// 將存檔的數(shù)據(jù)寫入文件
[data writeToFile:path atomically:YES];

恢復(fù)（解碼）
// 從文件中讀取數(shù)據(jù)
NSData *data = [NSData dataWithContentsOfFile:path];
// 根據(jù)數(shù)據(jù)，解析成一個(gè)NSKeyedUnarchiver對(duì)象
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person *person1 = [unarchiver decodeObjectForKey:@"person1"];
Person *person2 = [unarchiver decodeObjectForKey:@"person2"];
// 恢復(fù)完畢
[unarchiver finishDecoding];