Which component is responsible for animation: layer or view?

In iOS, animation is primarily managed by the layer (CALayer), which is the basic element of visualization. UIView is a higher-level object that contains a CALayer and manages its properties.

Animations are usually applied to CALayer properties, such as position, opacity, scale, etc. UIView provides convenient methods to start animations, but under the hood, they work with CALayer.

Thus, the layer (layer) is responsible for the animation, and UIView acts as a wrapper and provides a convenient interface for working with animations.