IOS 數(shù)據(jù)存儲詳解及實(shí)例代碼

沙盒根目錄：NSString *home = NSHomeDirectory();
Documents：(2種方式)
1. 利用沙盒根目錄拼接”Documents”字符串
//不建議采用，因?yàn)樾掳姹镜牟僮飨到y(tǒng)可能會修改目錄名
NSString *home = NSHomeDirectory();
NSString *documents = [home stringByAppendingPathComponent:@"Documents"];
2. 利用NSSearchPathForDirectoriesInDomains函數(shù)
// NSUserDomainMask 代表從用戶文件夾下找
// YES 代表展開路徑中的波浪字符“~”
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, NO);
// 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 *documents = [array objectAtIndex:0];
tmp：
NSString *tmp = NSTemporaryDirectory();
Library/Caches：
跟Documents類似的2種方法:
1. 利用沙盒根目錄拼接”Caches”字符串
2. 利用NSSearchPathForDirectoriesInDomains函數(shù)(將函數(shù)的第2個(gè)參數(shù)改為：NSCachesDirectory即可)
Library/Preference：
通過NSUserDefaults類存取該目錄下的設(shè)置信息

/ /獲取路徑
NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
path = [path stringByAppendingPathComponent:@"save.plist"];
/ /將數(shù)據(jù)封裝成字典
//不能存儲對象
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"小黃" forKey:@"name"];
[dict setObject:@"12345678" forKey:@"phone"];
[dict setObject:@"24" forKey:@"age"];
// 將字典持久化到Documents/save.plist文件中
[dict writeToFile:path atomically:YES];

讀取屬性列表，恢復(fù)NSDictionary對象
// 讀取Documents/save.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"]);

//比如，保存用戶名、字體大小、是否自動登錄
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"mr.zk" forKey:@"username"];
[defaults setFloat:18.0f forKey:@"text_size"];
[defaults setBool:YES forKey:@"auto_login"];

//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"];

NSString *path = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
path = [path stringByAppendingPathComponent:@"array.data"];
NSArray *array = [NSArray arrayWithObjects:@”a”,@”b”,nil];
[NSKeyedArchiver archiveRootObject:array toFile:path];

NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

NSKeyedArchiver-歸檔Person對象（Person.h）
@interface Person : NSObject<NSCoding>
@property (nonatomic, strong) 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 = @"zk";
person.age = 24;
person.height = 1.73f;
[NSKeyedArchiver archiveRootObject:person toFile:path];
//恢復(fù)(解碼)
Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

//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對象
NSKeyedArchiver *archiver = [[[NSKeyedArchiver alloc] initForWritingWithMutableData:data] autorelease];
// 開始存檔對象，存檔的數(shù)據(jù)都會存儲到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對象
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person *person1 = [unarchiver decodeObjectForKey:@"person1"];
Person *person2 = [unarchiver decodeObjectForKey:@"person2"];
// 恢復(fù)完畢
[unarchiver finishDecoding];