Adding State

By the end of this guide, you will:

• Define a Model using Data.define to hold your app state

• Explain why state is stored in a struct, not instance variables

• Pass the Model to your VIEW function

• Display dynamic content based on state

• Use model.with(...) to create updated state immutably

• Use predicate helpers (.up?, .down?, .j?, .k?) for key checks

• Use pattern matching (case message) for complex message handling

• Return a new Model from UPDATE with state changes

• Navigate your file browser with arrow keys and vim keys

• Understand when to use predicates vs pattern matching

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