tiger6688 / coregraphicsdynamicanimation

Dynamic drawRect: animation using CoreAnimation for interpolation.

#The What A neat sample project for dynamically animating in CoreAnimation anything drawn in drawRect: using CoreGraphics.

#The How Using some hand-waving, documentation reading, and internet browsing, I've distilled the steps required for this method to work down into the following recipe:

You'll find the following recipe documented in-context in the TOLLightLayer.m class:

1. @dynamic <property_name> - Let CoreAnimation generate the properties accessors at runtime for our animatable properties.
2. initWithLayer: - Let CoreAnimation make multiple copies of this layer to use as the presentation layer. Similar to a copyWithZone: implementation. Many layer copies are used for presentation interpolation.
3. needsDisplayForKey: - Tells CoreAnimation we need to re-draw for our custom animatable property when it is "changed" (always YES for now -- whether or not always returning YES is necessary or if it can be conditional).
4. actionForKey: - Return an explicit animation (action) for our custom attribute so that CoreAnimation has something to interpolate. Animation curve, timing, etc all have an effect on how many times drawRect: is called.
5. drawInContext: - Draw your stuff based on parameters (properties) that this layer accepts as input and that has been parameterized in the above method implementations.
6. Profit?

@theonlylars