decodeObjectForKey：總是返回零

Question

我試圖將我的對象圖保存到一個文件，然後在稍後重新加載它，但是decodeObjectForKey：對於我指定的任何鍵總是返回nil。

創建了一個二進制文件，它偶爾還有人類可讀的文本，即titleTextColor，所以我認爲歸檔過程正在工作。

我想知道NSKeyedArchiver和NSKeyedUnarchiver的工作原理嗎？任何幫助，將不勝感激。

- (void)encodeWithCoder:(NSCoder *)encoder { 
    [encoder encodeFloat:titleFontSize forKey:@"titleFontSize"]; 
    [encoder encodeObject:[UIColor orangeColor] forKey:@"titleTextColor"]; 
    [encoder encodeObject:lineSeparatorColor forKey:@"lineSeparatorColor"]; 
    [encoder encodeObject:bodyTextColor forKey:@"bodyTextColor"]; 
    [encoder encodeFloat:bodyTextFontSize forKey:@"bodyTextFontSize"]; 
    [encoder encodeObject:backgroundColor forKey:@"backgroundColor"]; 
    [encoder encodeObject:tintColor forKey:@"tintColor"]; 
    [encoder encodeInteger:bodyTextAlignment forKey:@"bodyTextAlignment"]; 

    [encoder encodeObject:@"Text" forKey:@"Text"]; 
} 

+ (void) saveToFile { 
    // Get the shared instance 
    PSYDefaults *sharedInstance = [PSYDefaults sharedInstance];  

    // Serialise the object 
    NSData *serializedObject = [NSKeyedArchiver archivedDataWithRootObject:sharedInstance]; 

    // Get the path and filename of the file 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *pathAndFileName = [documentsDirectory stringByAppendingPathComponent:ksDefaultsFileName]; 

    // Write the defaults to a file 
    if (serializedObject) [serializedObject writeToFile:pathAndFileName atomically:YES]; 
} 

+ (void) loadFromFile { 
    // Get the shared instance 
    PSYDefaults *sharedInstance = [PSYDefaults sharedInstance];  

    // Get the path and filename of the file 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *pathAndFileName = [documentsDirectory stringByAppendingPathComponent:ksDefaultsFileName]; 

    NSData *codedData = [[[NSData alloc] initWithContentsOfFile:pathAndFileName] autorelease]; 
    NSKeyedUnarchiver *defaults = [[NSKeyedUnarchiver alloc] initForReadingWithData:codedData]; 

    // Set the properties of the shared instance 
    NSString *test = [defaults decodeObjectForKey:@"Text"]; 
    NSLog (@"%@", test); 
    sharedInstance.titleTextColor = [defaults decodeObjectForKey:@"titleTextColor"]; 

    [defaults release]; 
} 

編輯：根據意見從DarkDust：

- (id)initWithCoder:(NSCoder *)aDecoder { 
    self = [super init]; 
    if (self) { 
     self.titleFontSize = [[aDecoder decodeObjectForKey:@"titleFontSize"] floatValue]; 
     self.titleTextColor = [aDecoder decodeObjectForKey:@"titleTextColor"]; 
     self.lineSeparatorColor = [aDecoder decodeObjectForKey:@"lineSeparatorColor"]; 
     self.bodyTextColor = [aDecoder decodeObjectForKey:@"bodyTextColor"]; 
     self.bodyTextFontSize = [[aDecoder decodeObjectForKey:@"bodyTextFontSize"] floatValue]; 
     self.backgroundColor = [aDecoder decodeObjectForKey:@"backgroundColor"]; 
     self.tintColor = [aDecoder decodeObjectForKey:@"tintColor"]; 
     self.bodyTextAlignment = [[aDecoder decodeObjectForKey:@"bodyTextAlignment"] intValue]; 
    } 
    return self; 
} 

，只是測試創建一個新的實例：

+ (void) loadFromFile { 
    // Get the shared instance 
    PSYDefaults *sharedInstance = [PSYDefaults sharedInstance];  

    // Get the path and filename of the file 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *pathAndFileName = [documentsDirectory stringByAppendingPathComponent:ksDefaultsFileName]; 

    NSData *codedData = [[[NSData alloc] initWithContentsOfFile:pathAndFileName] autorelease]; 
    PSYDefaults *newInstance = [NSKeyedUnarchiver unarchiveObjectWithData:codedData]; 

    sharedInstance.titleTextColor = newInstance.titleTextColor; 
} 

編輯 - 更新（需要編碼花車和ints as NSNumbers）

- (void)encodeWithCoder:(NSCoder *)encoder { 
    [encoder encodeObject:[NSNumber numberWithFloat:titleFontSize] forKey:@"titleFontSize"]; 
    [encoder encodeObject:titleTextColor forKey:@"titleTextColor"]; 
    [encoder encodeObject:lineSeparatorColor forKey:@"lineSeparatorColor"]; 
    [encoder encodeObject:bodyTextColor forKey:@"bodyTextColor"]; 
    [encoder encodeObject:[NSNumber numberWithFloat:bodyTextFontSize] forKey:@"bodyTextFontSize"]; 
    [encoder encodeObject:backgroundColor forKey:@"backgroundColor"]; 
    [encoder encodeObject:tintColor forKey:@"tintColor"]; 
    [encoder encodeObject:[NSNumber numberWithInt:bodyTextAlignment] forKey:@"bodyTextAlignment"]; 
} 

Answer 1

使用單個根對象序列化的數據進行解碼，但您嘗試使用不在該水平存在的一鍵反序列化。

你想unarchiveObjectWithData:，如：

NSData *codedData = [[[NSData alloc] initWithContentsOfFile:pathAndFileName] autorelease]; 
PSYDefaults *decodedDefaults = [NSKeyedUnarchiver unarchiveObjectWithData:codedData]; 

請注意，您還需要實現initWithCoder:作爲對口encodeWithCoder:。儘管看起來你想在這裏有一個單身人士，NSCoding要求在[NSKeyedArchiver archivedDataWithRootObject:sharedInstance]之前創建一個新對象。

，而無需創建的PSYDefaults一個新的實例。如果你想EN /解碼領域，那麼你需要使用-[NSKeyedArchiver initForWritingWithMutableData:]和存檔傳遞給類似的方法你encodeWithCoder:（但你應該給它一個不同的名稱，然後）。然後你會寫一個對方，通過NSKeyedUnarchiver讀取字段，在那裏你使用decodeObjectForKey:和每個字段的朋友。

您也可能想要閱讀Apple的Archives and Serializations Programming Guide。

Answer 2

嘗試使用，以節省您的對象：

[NSKeyedArchiver archiveRootObject:object toFile:filePath]; 

，並使用加載：

[NSKeyedUnarchiver unarchiveObjectWithFile:filePath]; 

我用上面的方法與自定義對象保存的NSDictionary到一個文件中。

而且你應該在你的對象中有函數initWithCoder：（NSCoder *）解碼器。 使用哪個

[decoder decodeObjectFoyKey:yourKey]; 

Answer 3

我有另一個問題NSCoder'sdecodeObjectForKey方法，而使用FXForm - 它崩潰沒有任何解釋。

- (id)initWithCoder:(NSCoder *)decoder 
{ 
    if (self = [super init]) { 
    self.someObject = [decoder decodeObjectForKey:@"someObject"]; 
    } 
    return self; 
} 

原因是內存問題。通常，看起來像沒有日誌中的錯誤解釋，這意味着，這是一個內存問題。我忘了使用正確的屬性 - 複製。我用assign來代替。這是正確的代碼：

@interface MyClass : : NSObject <FXForm, NSCoding> 

@property (nonatomic, copy) SomeClass *someObject; 

@end 

以防萬一有人遇到這個問題了。