iPhone：在應用程序被終止時保留NSUserDefaults值

Question

我正在嘗試使用NSUserDefaults實現「添加到收藏夾」功能。到目前爲止，我已經編寫了以下代碼

- (void)favouriteButtonClicked:(id)sender 
{ 
favselected = !favselected; // favselected is BOOL property 
MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate]; 
NSString* viewname = @"custom"; 

if(favselected) { 
    [favButton setBackgroundImage:[UIImage imageNamed:@"selected.png"] forState:UIControlStateNormal]; 
    [appDelegate addTOFavourites:self.ViewID viewType:self.ViewType]; 
} else { 
    [favButton setBackgroundImage:[UIImage imageNamed:@"unselected.png"] forState:UIControlStateNormal]; 
    [appDelegate removeFromFavourites:self.ViewID viewType:self.ViewType]; 
} 
} 

它只要工作細如我的應用程序正在運行，當我殺了我的申請，我失去這樣當下次查看裝入，在viewload isAddedToFavorites方法返回false我所有的存儲值。無論如何保存我的價值觀？我錯過了什麼嗎？

if([appDelegate isAddedToFavorites:self.ViewID]) { 
     [favButton setBackgroundImage:[UIImage imageNamed:@"selected.png"] forState:UIControlStateNormal]; 
     favselected = YES; 
    } else { 
     [favButton setBackgroundImage:[UIImage imageNamed:@"unselected.png"] forState:UIControlStateNormal]; 
     favselected = NO; 
    } 

編輯：

我試圖使用的NSMutableDictionary作爲我必須添加多個鍵值但下面的方法總是甚至添加對象字典之後顯示計數= 0。任何幫助將非常感激。謝謝。

-(BOOL)isAddedToFavorites:(NSString*)viewID { 
NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults]; 
NSMutableDictionary *favourites = [[standardUserDefaults objectForKey:kFavouriteItemsKey] mutableCopy]; 

if(favourites && [[favourites objectForKey:kFavouriteItemsKey] objectForKey:viewID]) 
    return YES; 

return NO; 
} 

-(void)addToFavourites:(NSString*)viewID viewType:(NSString*)viewType { 

NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults]; 
NSMutableDictionary *dict = [[standardUserDefaults objectForKey:kFavouriteItemsKey] mutableCopy]; 

if(standardUserDefaults) { 
    if(![dict objectForKey:viewID]) 
     [dict setObject:viewType forKey:viewID]; // It is coming here but still count zero! 

    NSLog(@"count = %d", [dict count]); 

    [standardUserDefaults setObject:dict forKey:kFavouriteItemsKey]; // Always dict remains null with 0 objects in it 
    [standardUserDefaults synchronize]; 
    [dict release]; 
} 
} 

-(void)removeFromFavourites:(NSString*)viewID viewType:(NSString*)viewType { 

NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults]; 
NSMutableDictionary *dict = [[standardUserDefaults objectForKey:kFavouriteItemsKey] mutableCopy]; 

if(standardUserDefaults) { 
    if ([dict objectForKey:viewID]) 
     [dict removeObjectForKey:viewID]; 

    [standardUserDefaults setObject:dict forKey:kFavouriteItemsKey]; 
    [standardUserDefaults synchronize]; 
    [dict release]; 
} 
} 

謝謝。

Answer 1

NSUserDefaults實際上用於永久存儲值，實際上如果您爲程序創建任何設置，它們將被保存爲NSUserDefaults。

我認爲問題在於您沒有使用您正在檢索的相同密鑰來保存它。嘗試保存這樣的：

//To save 
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; 
    [defaults setObject:appDefaults forKey:kFavouriteItemsKey]; 
    [[NSUserDefaults standardUserDefaults] synchronize]; 

    //To retrieve 
NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults]; 
NSMutableDictionary *favourites = [[standardUserDefaults objectForKey:kFavouriteItemsKey] mutableCopy]; 

對於詞典嘗試：

NSDictionary *myDictionary= [[NSUserDefaults standardUserDefaults] objectForKey:kFavouriteItemsKey]; 

     // Create a mutable dictionary to replace the old immutable dictionary 
    NSMutableDictionary *myMutableDictionary= [NSMutableDictionary dictionaryWithCapacity:[myDictionary count]+1]; 

     // transfer the old dictionary into the new dictionary 
    [myMutableDictionaryaddEntriesFromDictionary:myDictionary]; 

     // Now add the data 
    [myMutableDictionary setObject:myObject forKey:myKey];