iOS 數(shù)據(jù)持久性存儲(chǔ)--屬性列表存儲(chǔ)

iOS上常用四種數(shù)據(jù)存取方法有:

屬性列表

對(duì)象歸檔

iOS的嵌入式關(guān)系數(shù)據(jù)庫(kù)(SQLite3)

蘋(píng)果公司提供持久性共聚Core Data

它們的應(yīng)用程序都有自己的/Documents文件夾，各自的應(yīng)用程序只能讀寫(xiě)自己的/Documents目錄內(nèi)容

1.創(chuàng)建一個(gè)新工程叫PersistenceDemo； File->New->Project ->single View Application -> next

2.在PersistenceViewController.h文件聲明輸出口和和實(shí)例方法

#import <UIKit/UIKit.h>  @interface PersistenceViewController : UIViewController  @property (weak, nonatomic) IBOutlet UITextField *field1; @property (weak, nonatomic) IBOutlet UITextField *field2; @property (weak, nonatomic) IBOutlet UITextField *field3; @property (weak, nonatomic) IBOutlet UITextField *field4;  -(NSString *)dataFilePath; -(void)applicationWillResignActive:(NSNotification *)notification;  @end

4.在對(duì)應(yīng)的.m文件中

dataFilePath將kFileName串聯(lián)到Documents目錄的路徑，以創(chuàng)建并返回?cái)?shù)據(jù)文件的完整路徑名

-(NSString *)dataFilePath {     /*常量NSDocumentDirectory表明我們正在查找Documents目錄路徑，第二個(gè)常量NSUserDomainMask表示的是把搜索范圍定在應(yīng)用程序沙盒中，YES表示的是希望希望該函數(shù)能查看用戶主目錄*/          NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); //  數(shù)組索引0處Documentd目錄，       NSString *documentDirectory = [paths objectAtIndex:0]; //    返回一個(gè)kFileName的完整路徑     return [documentDirectory stringByAppendingPathComponent:kFileName]; }

- (void)viewDidLoad {     [super viewDidLoad]; //  檢查數(shù)據(jù)文件是否存在，不存在則不加載       NSString *filePath = [self dataFilePath];     if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {         NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];                  field1.text = [array objectAtIndex:0];         field2.text = [array objectAtIndex:1];         field3.text = [array objectAtIndex:2];         field4.text = [array objectAtIndex:3];     } //    注冊(cè)一個(gè)通知，按下home鍵，執(zhí)行applicationWillResignActive:方法     UIApplication *app = [UIApplication sharedApplication];     [[NSNotificationCenter defaultCenter]addObserver:self                                             selector:@selector(applicationWillResignActive:)                                                 name:UIApplicationWillTerminateNotification                                               object:app];      	 }

//當(dāng)按下home鍵的時(shí)候調(diào)用這個(gè)方法 -(void)applicationWillResignActive:(NSNotification *)notification {     NSMutableArray *array = [[NSMutableArray alloc] init];     [array addObject:field1.text];     [array addObject:field2.text];     [array addObject:field3.text];     [array addObject:field4.text]; //    將TextField中數(shù)據(jù)寫(xiě)入到屬性表之中     [array writeToFile:[self dataFilePath] atomically:YES]; }

Notification對(duì)象非常簡(jiǎn)單. 它就是poster要提供給observer的信息包裹. notification對(duì)象有兩個(gè)重要的成員變量: name 和 object. 一般object都是指向poster(為了讓observer在接受到notification時(shí)可以回調(diào)到poster)
所以,notification有兩個(gè)方法
    - (NSString *)name
    - (id)object
NSNotificaitonCernter是架構(gòu)的大腦了.它允許我們注冊(cè)observer對(duì)象, 發(fā)送notification, 撤銷observer對(duì)象注冊(cè)
下面是它的一些常用方法
+ (NSNotificationCenter *)defaultCenter
返回notification center [類方法,返回全局對(duì)象, 單件模式.cocoa的很多的全局對(duì)象都是通過(guò)類似方法實(shí)現(xiàn)]

- (void)addObserver:(id)anObserver
           selector:(SEL)aSelector
               name:(NSString *)notificationName
             object:(id)anObject

注冊(cè)anObserver對(duì)象:接受名字為notificationName, 發(fā)送者為anObject的notification. 當(dāng)anObject發(fā)送名字為notificationName的notification時(shí), 將會(huì)調(diào)用anObserver的aSelector方法,參數(shù)為該notification. 如果notificationName為nil. 那么notification center將anObject發(fā)送的所有notification轉(zhuǎn)發(fā)給observer
. 如果anObject為nil.那么notification center將所有名字為notificationName的notification轉(zhuǎn)發(fā)給observer

- (void)postNotification:(NSNotification *)notification
發(fā)送notification至notification center
- (void)postNotificationName:(NSString *)aName
                      object:(id)anObject

創(chuàng)建并發(fā)送一個(gè)notification
- (void)removeObserver:(id)observer
移除observer

引用 http://blog.csdn.net/zhanglei5415/article/details/6454940

源代碼:http://download.csdn.net/detail/duxinfeng2010/4445711