is there a way to run 2 NSAnimation objects simultaneously?

cocoa, core-image, nsanimation, objective-c, osx-lion

Solution

`NSAnimation` is not really the best choice for animating multiple objects and their properties simultaneously.

Instead, you should make your views conform to the `NSAnimatablePropertyContainer` protocol.

You can then set up multiple custom properties as animatable (in addition to the properties already supported by `NSView`), and then you can simply use your views' `animator` proxy to animate the properties:

yourObject.animator.propertyName = finalPropertyValue;

Apart from making animation very simple, it also allows you to animate multiple objects simultaneously using an `NSAnimationContext`:

[NSAnimationContext beginGrouping];
firstObject.animator.propertyName = finalPropertyValue1;
secondObject.animator.propertyName = finalPropertyValue2;
[NSAnimationContext endGrouping];

You can also set the duration and supply a completion handler block:

[NSAnimationContext beginGrouping];
[[NSAnimationContext currentContext] setDuration:0.5];
[[NSAnimationContext currentContext] setCompletionHandler:^{
    NSLog(@"animation finished");
}];
firstObject.animator.propertyName = finalPropertyValue1;
secondObject.animator.propertyName = finalPropertyValue2;
[NSAnimationContext endGrouping];

The `NSAnimation` and `NSViewAnimation` classes are much older than the animator proxy support and I highly recommend that you move away from them if possible. Supporting the `NSAnimatablePropertyContainer` protocol is much simpler than managing all the `NSAnimation` delegate stuff. The Lion support for custom timing functions and completion handlers means there's really no need to do that any more.

For a standard `NSView` object, if you want to add animation support to a property in your view, you just need to override the `+defaultAnimationForKey:` method in your view and return an animation for the property:

//declare the default animations for any keys we want to animate
+ (id)defaultAnimationForKey:(NSString *)key
{
    //in this case, we want to add animation for our x and y keys
    if ([key isEqualToString:@"x"] || [key isEqualToString:@"y"]) {
        return [CABasicAnimation animation];
    } else {
        // Defer to super's implementation for any keys we don't specifically handle.
        return [super defaultAnimationForKey:key];
    }
}

I've created a simple sample project that shows how to animate multiple properties of a view simultaneously using the `NSAnimatablePropertyContainer` protocol.

All your view needs to do to update successfully is make sure that `setNeedsDisplay:YES` is called when any of the animatable properties are modified. You can then get the values of those properties in your `drawRect:` method and update the animation based on those values.

If you want a simple progress value that is analogous to the way things work with `NSAnimation`, you could define a `progress` property on your view and then do something like this:

yourView.progress = 0;
[yourView.animator setProgress:1.0];

You can then access `self.progress` in your `drawRect:` method to find out the current value of the animation.

Problem

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