Problem Statement
What is the purpose of the Consumer widget in Provider?
Explanation
Consumer widget listens to a Provider and rebuilds only its subtree when the provided value changes, enabling fine-grained control over what rebuilds. Instead of rebuilding an entire widget when using Provider.of with listen: true, Consumer rebuilds only the specific parts that depend on the data, improving performance by minimizing unnecessary rebuilds.
Consumer takes a builder function with three parameters: context, value (the provided data), and child (an optional static subtree that doesn't rebuild). The builder returns the widget tree that should rebuild when data changes. The child parameter is an optimization - pass widgets that don't depend on the changing data as child, and they'll be reused without rebuilding.
You can use Consumer, Consumer2, Consumer3, etc., for listening to multiple providers simultaneously. Use Consumer when you need to rebuild specific parts of the widget tree based on state changes, and use context.watch for simpler cases where the entire widget should rebuild. Consumer provides better performance optimization through its child parameter.
