@@ -727,6 +727,28 @@ With function builders, you can even create your own DSLs. And this year in WWDC
727727Apple released more features based on function builders, like **WidgetKit ** and
728728SwiftUI **App Structure **.
729729
730+ How SwiftUI determine when to update a view?
731+ --------------------------------------------
732+ All views in SwiftUI are like **PureComponent ** in React by default. That means,
733+ all the member variables (props) will be used to evaluate the equality, of course
734+ it's shallow comparison.
735+ 736+ What if you want to customize the update strategy? If you take a look at the
737+ declaration of ``View `` protocol, you will notice this subtle thing:
738+ 739+ .. code-block :: swift
740+
741+ extension View where Self : Equatable
742+
743+ /// Prevents the view from updating its child view when its new value is the
744+ /// same as its old value.
745+ @inlinable public func equatable () -> EquatableView<Self >
746+ }
747+
748+ SwiftUI provides an ``EquatableView `` to let you achieve that. All you need to do
749+ is make your view type conform ``Equatable `` and implement the ``== `` function.
750+ Then wrap it into ``EquatableView `` at the call-site.
751+ 730752.. References:
731753
732754.. _`Thinking in React Hooks` : https://wattenberger.com/blog/react-hooks
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