DejalObject: an abstract data model class that can represent subclasses as dictionary or JSON data

DejalObject is an abstract data model class that can represent subclasses as dictionary or JSON data for saving to disk or over the network.

Included are DejalColor, DejalDate and DejalInterval concrete subclasses.

They work on both OS X and iOS.


  • DejalObject: This is an abstract subclass of NSObject that adds methods to represent the receiver as a dictionary or JSON data, load default values, track changes, enumerate an array of DejalObject instances, and more.
  • DejalColor: A concrete subclass of DejalObject to represent a color (for OS X or iOS), enabling it to be stored in a DejalObject subclass.
  • DejalDate: Another concrete subclass to represent a date, primarily so it can automatically be represented as JSON.
  • DejalInterval: A subclass to represent a time interval or a range of intervals, including an amount and units, with methods to represent the interval or range in various ways, including as human-readable strings (see also the DejalIntervalPicker project for OS X).

A demo project is included, showing a subclass of DejalObject to store various data types.


Include at least DejalObject.h and DejalObject.m in your project. Include the DejalColor, DejalDate and/or DejalInterval files if those are needed.

Add a new class that inherits from DejalObject.

In the header, you only need to define properties to store, e.g.:

@interface Demo : DejalObject

@property (nonatomic, strong) NSString *text;  
@property (nonatomic) NSInteger number;  
@property (nonatomic, strong) DejalColor *label;  
@property (nonatomic, strong) DejalDate *when;


In the implementation, override -initWithCoder: and -encodeWithCoder: if you need to support coding (secure coding is supported in DejalObject).

Override -loadDefaultValues to populate default values to each of the properties. A version number can be assigned (via DejalObject’s version property) to enable upgrading later, e.g.:

- (void)loadDefaultValues;  
    [super loadDefaultValues];

    self.version = DemoVersion;  
    self.text = @"Foo";  
    self.number = 12345;  
    self.label = [DejalColor colorWithColor:[NSColor blueColor]];  
    self.when = [DejalDate dateWithNow];  

Finally, override -savedKeys to indicate which properties should be automatically included in the dictionary or JSON representation, e.g.:

- (NSArray *)savedKeys;  
    return [[super savedKeys] arrayByAddingObjectsFromArray:@[@"text", @"number", @"label", @"when"]];  

A DejalObject subclass can be represented as a NSDictionary simply by invoking the dictionary property on it, or as JSON via the json property. That can then be saved to disk or the user defaults, or passed over the network.

Those properties can also be set, or a new instance can be created via +objectWithDictionary: or +objectWithJSON:, or an instance with default values via +object.

DejalObject instances automatically track changes, with a hasChanges BOOL property indicating that something has changed (so may need to be saved). There is also a hasAnyChanges property that recursively enumerates the properties and any other DejalObject instances in them, e.g. if the color is changed in the above example.

After saving, you should invoke -clearChanges to reset the change flag.

You can get the code and more information from the Dejal Open Source page.

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