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What is the role of the key path in Core Animation?

I'm going to get to know Core Animation and try to implement a simple movement along a curve line. I found a really useful piece of code here

There is a line:

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];

Why do we need this property called keyPath? What is his role? The code only works when using the proposed NSString @ position and nothing more. So is this an inline constant string? It doesn’t look like that. I hope you see my confusion. Could you please explain in simple terms how I can manage this KeyPath property?

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2 answers
  • KeyPath says which animation attribute will be changed before creating an animation effect.
  • You can use any of the animation properties as a key path.
  • You can find them in the header file (say, CALayer) on which you apply the animation
  /* The position in the superlayer that the anchor point of the layer's bounds rect is aligned to. Defaults to the zero point. **Animatable**. */ 
  @property CGPoint position;
  • Not a String constant, this is an attribute name
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CABasicAnimation and CAKeyframeAnimation inherit from CAPropertyAnimation. Both use the animationWithKeyPath: method.

KeyPath must contain Animation properties . Find them here Link

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Source: https://habr.com/ru/post/1401559/

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