Philosophy Edit on GitHub
Components are immutable objects that specify how to configure views.
A simple analogy is to think of a component as a stencil: a fixed description that can be used to paint a view but that is not a view itself. A component is often composed of other components, building up a component hierarchy that describes a user interface.
Let’s see some sample code for rendering an article in a news app:
Components have three characteristics:
Declarative: Instead of implementing
-layoutSubviewsand positioning subviews manually, you declare the subcomponents of your component (here, we say “stack them vertically”).
Functional: Data flows in one direction. Methods take data models and return totally immutable components. When state changes, ComponentKit re-renders from the root and reconciles the two component trees from the top with as few changes to the view hierarchy as possible.
FooterComponentis used in an article, but it could be reused for other UI with a similar footer. Reusing it is a one-liner.
CKStackLayoutComponentis inspired by the flexbox model of the web and can easily be used to implement many layouts.