Key-Value Observing

KVO helper provides changed notification and objects binding method with blocks.
Note: if your object is using KVO helper and has its own dealloc methods, please put [self A_RemoveObservings] in it.

The demo model structure

            // TestDataModel
            @interface TestDataModel : A_DataModel
            @property (retain, nonatomic) NSString* Name;
            @property (retain, nonatomic) NSNumber* ID;
            @end

            // ExampleModel
            @interface ExampleModel : NSObject
            @property (strong, nonatomic) TestDataModel* model;
            @property (nonatomic) int times;
            @end
        

Add Observer Example

    /* Add an observer. In the default,
    it's using NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew options. */
    TestDataModel* _model = [[TestDataModel alloc] init];
    [_model A_AddObserver:@"Name" block:^(TestDataModel *itself, NSDictionary *change) {
        XCTAssertTrue([[change objectForKey:@"new"] isEqualToString:@"A"]);
    }];
    [_model setName:@"A"]; 

    // You can also setup your Observing Option
    [_model A_AddObserverWithOption:NSKeyValueObservingOptionNew
             Key:@"ID" block:^(TestDataModel *itself, NSDictionary *change) {
        // [change objectForKey:@"new"] is the new value
    }];

    // With an assist parameter:
    [_model A_AddObserver:@"ID" Param:@"The Message"
                block:^(TestDataModel *itself, NSDictionary *change, id param) {

        [A_TaskHelper A_RunInMainWithParam:param Block:^(id arg) {

            [UIAlertView A_DisplyAlert:[NSString stringWithFormat:@"%@",arg]
                              AndTitle:@"Changed Notice"
                          CancelButton:@"Okay"];

        }];

    }];

Remove Observer Example

    //Remove the observer of Name
    [_model A_RemoveObserver:@"Name"];

    // Remove all observers
    [_model A_RemoveAllObservers];
        

Binding Example

        ExampleModel* example = [[ExampleModel alloc] init];
        [example A_Bind:@"times" To:@"model.ID"];

        example.times = 1;
        // example.model.ID => (NSNumber)(int)1

        // Binding method provides covert block
        ExampleModel* example = [[ExampleModel alloc] init];
        /* the type of covert block is ^id(id value), please modify to corresponding type;
           in this case, it should be ^NSString(int value)*/
        [example A_Bind:@"times" To:@"model.Name" Convert:^NSString(int value) {
            return [NSString stringWithFormat:@"The times is %@",value];
        }];

        example.times = 1;
        // example.model.Name => (NSString)@"The times is 1"

        // Crossing object binding
        ExampleModel* example1 = [[ExampleModel alloc] init];
        ExampleModel* example2 = [[ExampleModel alloc] init];
        [example1 A_Bind:@"model.Name" ToTager:example2 AndKey:@"model.Name"];

        [example1.model setName:@"Test"];
        // example2.model.Name => Same as example1.model.Name (NSString)@"Test" 

Remove Binding Example

    //Remove binding is same as remove Observer
            [_model A_RemoveBinding:@"model.Name"];

            // Remove all binding
            [_model A_RemoveAllBinding];