Lesson 2.1

This lesson will teach you:

• Converting stateful class components to function components using hooks

The goal for this lesson is to get experience working with React Class components and how to get the same functionality from a class component and a functional component using hooks.

The React application that you will be using is a simple number guessing game. The game is currently written using a mix of class components for components that have state and stateless functional components.

When you are done the application should have all of the same functionality, but the class components should be refactored to be function components that use the useState hook to manage their stateful data.

Instructions

Fork the repository

The first step is to fork the source repository in GitHub and then clone your forked repository to your local development system. There are instructions for forking a repository in GitHub here: https://docs.github.com/en/get-started/quickstart/fork-a-repo

The repository to fork is: https://github.com/Code-the-Dream-School/ctd-react-numberGuessingAssignment

Once you have forked it and cloned locally make sure that the application runs by running the following commands if you are using yarn:

If you are using npm just replace yarn with npm and run the same commands.

yarn install
yarn start

Familiarize yourself with the code

In the current version of the application there is a mix of class components and stateless function components. Take some time to look over the structure of the application so that you understand how it is constructed.

The class components in the current version are NumberGuessingGame and GuessControl. These are the components that you will be converting to be function components with hooks. The existing function components don't need any changes.

If you want to attempt this on your own without a step by step walkthrough first then leave the section below collapsed.

Step by Step

Click the arrow to expand this section and see step by step instructions to convert to function components with hooks.

Convert GuessControl

• Open the GuessControl.js file.
• Rename the current GuessControl class to GuessControlOld if you want to keep it a reference while converting the code.
• Create a new function component called GuessControl that will take an onGuess prop.
• Copy the return value from the render function in the class component to be the return value in the new function component. Remove any references to this. since those will be replaced with new references to local variables or props passed in to the function component.
• Create a new state variable named currentGuess with setter setCurrentGuess and default value of an empty string. Set the value property for the input element to refer to this state value. (Make sure to import useState)
• Create a handleInputChange function within the component that updates the currentGuess state value when the user changes the value in the input. Set the onChange property for the input element to refer to this function.
• Create a onSubmitGuess function that calls the onGuess prop with the currentGuess value converted to a number and also resets the currentGuess to an empty string when it is called. Set the onClick property on the button to refer to this function.
• If you still have the old class version around as GuessControlOld, delete it.

Convert NumberGuessingGame

• Open the NumberGuessingGame.js file.
• Rename the current NumberGuessingGame class to NumberGuessingGameOld if you want to keep it a reference while converting the code.
• Create a new function component called NumberGuessingGame.
• Copy the logic and return value from the render function in the class component to be in the new function component. Remove any references to this. since those will be replaced with new references.
• Create 3 state variables and their setters for numberToGuess, numberOfGuesses, and latestGuess and initialize them to the same values from the class component version. (Make sure to import useState)
• Create a handleGuess function that will be passed in to the GuessControl component as the onGuess prop. This function should take the guess as an argument and set the latestGuess state with the guess (converted to a number using the Number function) and increment the numberOfGuesses state.
• Create a handleReset function within the component that resets all 3 of the state properties the same way the handleReset function from the class component reset them. Pass this function to the GameOver component as the onReset prop.
• Update all references from the class component that referred to this.<something> to refer to the correct variable or function for the new function component.
• If you still have the old class version around as NumberGuessingGameOld, delete it.