屏幕快照 2016-11-17 15.33.12.png
iOS數(shù)據(jù)存取的常見(jiàn)方式：
- XML屬性列表(plist)歸檔,通常的路徑是Documents
對(duì)象是NSDictionary碍拆、NSArray,就可以使用writeToFile:atomically:方法直接將對(duì)象寫(xiě)到屬性列表文件中
存
將數(shù)據(jù)封裝成字典
NSMutableDictionary *dic = [NSMutableDictionary dictionary];
[dic setObject:@"小紅" forKey:@"name"];
[dic setObject:@"15013141314" forKey:@"phone"];
[dic setObject:@"27" forKey:@"age"];
// 將字典持久化到Documents/stu.plist文件中
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filepath = [docPath stringByAppendingPathComponent:@"data.plist"];
[dic writeToFile:filepath atomically:YES];
// 或者是數(shù)組
// 注意:如果為YES則保證文件的寫(xiě)入原子性,就是說(shuō)會(huì)先創(chuàng)建一個(gè)臨時(shí)文件,直到文件內(nèi)容寫(xiě)入成功再導(dǎo)入到目標(biāo)文件里.
// 如果為NO,則直接寫(xiě)入目標(biāo)文件里.
讀
讀取Documents/stu.plist的內(nèi)容，實(shí)例化NSDictionary或者NSArray
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filepath = [docPath stringByAppendingPathComponent:@"data.plist"
];
NSDictionary *dic = [NSDictionary dictionaryWithContentsOfFile:path];
NSLog(@"name:%@", [dict objectForKey:@"name"]);
NSLog(@"phone:%@", [dict objectForKey:@"phone"]);
NSLog(@"age:%@", [dict objectForKey:@"age"]);
// 如果寫(xiě)入的是數(shù)組，就用下面的方法取值
NSArray *array= [NSArray arrayWithContentsOfFile:filepath];
- preference(偏好設(shè)置): 直接寫(xiě)到Library/Preferences:目錄下面;保存用戶(hù)名揪利、字體大小、是否自動(dòng)登錄.
存
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"itcast" forKey:@"username"];
[defaults setFloat:18.0f forKey:@"text_size"];
[defaults setBool:YES forKey:@"auto_login"];
// 注意：UserDefaults設(shè)置數(shù)據(jù)時(shí)狠持，不是立即寫(xiě)入疟位，而是根據(jù)時(shí)間戳定時(shí)地把緩存中的數(shù)據(jù)寫(xiě)入本地磁盤(pán)。所以調(diào)用了set方法之后數(shù)據(jù)有可能還沒(méi)有寫(xiě)入磁盤(pán)應(yīng)用程序就終止了喘垂，因此要調(diào)用synchronize方法強(qiáng)制寫(xiě)入
[defaults synchronize];
讀
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *username = [defaults stringForKey:@"username"];
float textSize = [defaults floatForKey:@"text_size"];
BOOL autoLogin = [defaults boolForKey:@"auto_login"];
- NSKeyedArchiver歸檔(NSCoding):可以存儲(chǔ)對(duì)象
(1) NSString甜刻、NSDictionary、NSArray正勒、NSData得院、NSNumber等類(lèi)型，可以直接用NSKeyedArchiver進(jìn)行歸檔和恢復(fù)
(2)不是所有的對(duì)象都可以直接用這種方法進(jìn)行歸檔章贞，只有遵守了<NSCoding>協(xié)議的對(duì)象才可以;
(3).NSCoding協(xié)議有2個(gè)方法:
一是:
encodeWithCoder:每次歸檔對(duì)象時(shí)祥绞，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，encodeObject:forKey:方法歸檔實(shí)例變量;
二是：
initWithCoder:每次從文件中恢復(fù)(解碼)對(duì)象時(shí)鸭限，都會(huì)調(diào)用這個(gè)方法蜕径。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;
// 首先要對(duì)對(duì)象實(shí)行下面方法:
- (void)encodeWithCoder:(NSCoder *)encoder{
[encoder encodeObject:self.no forKey:@"no"];
[encoder encodeInt:self.age forKey:@"age"];
[encoder encodeDouble:self.height forKey:@"height"];
}
- (id)initWithCoder:(NSCoder *)decoder
{ if (self = [super init]) {
// 讀取文件的內(nèi)容
self.no = [decoder decodeObjectForKey:@"no"];
self.age = [decoder decodeIntForKey:@"age"];
self.height = [decoder decodeDoubleForKey:@"height"];
}
return self;
}
存
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
// 獲得文件的全路徑
NSString *path = [doc stringByAppendingPathComponent:@"xxx.data"];
//將對(duì)象歸檔
[NSKeyedArchiver archiveRootObject:stu toFile:path];
讀
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *path = [doc stringByAppendingPathComponent:@"xxx.data"];
Student *stu = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
存取對(duì)象數(shù)組
存
NSMutableArray *itemsDataArray = [NSMutableArray array];
for (RWTItem *item in self.items) {
NSData *itemData = [NSKeyedArchiver archivedDataWithRootObject:item];
[itemsDataArray addObject:itemData];
}
[[NSUserDefaults standardUserDefaults] setObject:itemsDataArray forKey:kRWTStoredItemsKey];
[[NSUserDefaults standardUserDefaults] synchronize];
讀
NSArray *storedItems = [[NSUserDefaults standardUserDefaults] arrayForKey:kRWTStoredItemsKey];
self.items = [NSMutableArray array];
if (storedItems) {
for (NSData *itemData in storedItems) {
RWTItem *item = [NSKeyedUnarchiver unarchiveObjectWithData:itemData];
[self.items addObject:item];
}
}
