iOS 本機資料儲存(一)

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iOS 本機資料儲存(一)

 

本機資料儲存之UserDefaults

 

UserDefaults支援的基礎資料型別 (Elementary Data Type)包含:

NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary

 

對於自訂的類,如果直接儲存會出現如下錯誤:

Property list invalid for format (property lists cannot contain objects of type ‘CFType’)

 

如果想儲存自訂的類,需要對其進行編碼即轉換為基礎資料型別 (Elementary Data Type)。

 

類定義,以及轉換為NSDictionary類型:

 

@interface XYZToDoItem : NSObject@property NSString *itemName;@property BOOL completed;//@property (readonly) NSDate *creationDate;@property NSDate *creationDate;- (NSDictionary *) encodedItem;@end

 

 


@implementation XYZToDoItem#pragma Used for encoded objects to be able to save to UserDeafaults- (NSDictionary *) encodedItem{    return [NSDictionary dictionaryWithObjectsAndKeys:self.itemName, @itemName,            [NSNumber numberWithBool:self.completed], @completed,            self.creationDate , @creationDate, nil];}@end

 

 

調用的地方,儲存如UserDefault裡,並且讀取轉換為相應的類:
- (void) saveUserDefaultsOwn{    XYZToDoItem *item1 = [[XYZToDoItem alloc] init];    item1.itemName = @Buy milk;    //[self.toDoItems addObject:item1];    XYZToDoItem *item2 = [[XYZToDoItem alloc] init];    item2.itemName = @Buy eggs;    //[self.toDoItems addObject:item2];    XYZToDoItem *item3 = [[XYZToDoItem alloc] init];    item3.itemName = @Read a book;    //[self.toDoItems addObject:item3];            NSUserDefaults *userdefaults = [NSUserDefaults standardUserDefaults];    [userdefaults setObject:[item1 encodedItem] forKey:@item1];    [userdefaults setObject:[item2 encodedItem] forKey:@item2];    [userdefaults setObject:[item3 encodedItem]forKey:@item3];        [userdefaults synchronize];}- (void) readUserDeafultsOwn{    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];    NSDictionary *dic1 = [[NSDictionary alloc] init];            dic1 = [userDefaults objectForKey:@item1];        XYZToDoItem *item1 = [[XYZToDoItem alloc] init];    item1.itemName = [dic1 objectForKey:@itemName];    item1.completed = [dic1 objectForKey:@completed];    item1.creationDate = [dic1 objectForKey:@creationDate]; //initial it is readonly, not right    dic1 = [userDefaults objectForKey:@item2];    XYZToDoItem *item2 = [[XYZToDoItem alloc] init];    item2.itemName = [dic1 objectForKey:@itemName];    item2.completed = [dic1 objectForKey:@completed];    item2.creationDate = [dic1 objectForKey:@creationDate]; //initial it is readonly, not right        dic1 = [userDefaults objectForKey:@item2];    XYZToDoItem *item3 = [[XYZToDoItem alloc] init];    item3.itemName = [dic1 objectForKey:@itemName];    item3.completed = [dic1 objectForKey:@completed];    item3.creationDate = [dic1 objectForKey:@creationDate]; //initial it is readonly, not right        //XYZToDoItem *item2 = [userDefaults objectForKey:@item2];    //XYZToDoItem *item3 = [userDefaults objectForKey:@item3];        [self.toDoItems addObject:item1];    [self.toDoItems addObject:item2];    [self.toDoItems addObject:item3];}


綜上為簡單的對複雜的類進行簡單封裝並且讀取的例子。

 

 

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