Communication between components | Mastering React: An In-Depth Zero to Hero Video Series

Summary

In this React JS tutorial, the instructor guides beginners through component communication, focusing on parent-child relationships. Key concepts include passing state as props from parent to child and invoking parent functions from child components using callback props. The video also touches on the challenges of prop drilling and hints at the solution: using React's Context API, which will be explored in the next installment. The instructor concludes with a practical task, encouraging viewers to apply these concepts in a sample application and provides a repository link for solution code.

Takeaways

• 🎓 This video is part of a React JS tutorial series aimed at beginners learning React from scratch.
• 🔗 The previous video covered the useRef hook, while this one focuses on component communication.
• 👨‍👧 Demonstrates communication between parent and child components in React using a functional component example.
• 📝 Explains how to pass state from a parent component to a child component via props.
• 🔄 Shows the reverse scenario, updating the parent component's state based on user input in the child component.
• 📌 Highlights the importance of keeping state in the parent component to manage child component inputs.
• 🔧 Introduces callback functions as a method to invoke parent component functions from child components.
• 🔄 Discusses the challenge of invoking child component functions from a parent component and presents a solution using `useEffect` and props.
• 👥 Touches on the concept of 'props drilling' and its complexity when components are deeply nested.
• 📘 Sets up a task for viewers to practice component communication by creating an application with two child components and a parent component that interact.
• 🔗 Provides a link to a repository for solution code related to the task, encouraging further learning and practice.

Q & A

What is the main topic of the video?

The main topic of the video is communication between components in React JS, specifically focusing on how to manage state and pass data between parent and child components.

What is the purpose of creating a text box and state in the parent component?

The purpose of creating a text box and state in the parent component is to demonstrate how to pass the state as a prop to the child component, allowing the child to display the value of the text box from the parent.

How does the video show the reverse scenario of passing data from child to parent?

The video demonstrates passing data from child to parent by moving the state management to the parent component and passing a callback function as a prop to the child, which the child can use to update the parent's state.

What is the role of the callback function in the communication between parent and child components?

The callback function serves as a mechanism for the child component to communicate back to the parent by allowing the child to invoke a function defined in the parent, thus enabling two-way communication.

Why is it not straightforward to call a function in the child component from the parent component?

It is not straightforward because React components are designed to have a unidirectional data flow, and direct access to child components from the parent is not provided. This design encourages a clean separation of concerns and state management.

How does the video suggest invoking a function in the child component when a button in the parent is clicked?

The video suggests using the useEffect hook in the child component and passing a prop from the parent that changes upon button click. This change in prop triggers the useEffect, which in turn calls the function in the child component.

What is the term used for the process of passing data through multiple layers of components?

The process of passing data through multiple layers of components is referred to as 'props drilling' in the video.

What is the alternative to props drilling when components are deeply nested?

The alternative to props drilling is using React's Context API, which allows for sharing values between components without having to explicitly pass props through every level of the tree.

What task does the video assign to the viewers?

The task assigned to the viewers is to create an application where clicking a button in one child component changes the color of a div in another child component, and typing in a text box in one child updates the display in another child.

Where can the viewers find the solution code for the task mentioned in the video?

The viewers can find the solution code for the task in a repository, the link to which is provided in the video description.

Outlines

00:00

🛠️ Understanding Component Communication in React

This paragraph introduces the topic of component communication in React, specifically focusing on parent-child relationships. The instructor demonstrates how to pass state from a parent component to a child component using props. They also explore the reverse scenario, where the child component's input needs to be reflected in the parent. To achieve this, the state is maintained in the parent component, and a callback function is passed to the child component. The paragraph concludes with an example of invoking a parent component's function from a child component, using props and event handling.

05:01

🔄 Advanced Component Interactions and Context Introduction

In this paragraph, the focus shifts to more complex scenarios of component communication, such as communication between siblings. The instructor explains the concept of 'props drilling,' where data must be passed through multiple layers of components, which can become cumbersome. To address this, the instructor introduces the concept of 'context' in React, which will be elaborated upon in the next video. The paragraph ends with a practical task for viewers to implement a scenario involving parent and child components, where interactions between them lead to state changes in other components. The instructor also invites viewers to access the solution code from a provided repository link.

Keywords

💡React JS

React JS is a popular JavaScript library for building user interfaces, particularly for single-page applications. It is maintained by Facebook and a community of individual developers and companies. In the video, React JS is the central theme as the series aims to teach beginners how to build applications from scratch using this library.

💡Zero to Hero series

This phrase suggests a comprehensive learning series that starts with the basics and progresses to advanced concepts. In the context of the video, it refers to the educational content designed for beginners who are new to React JS and want to become proficient in it.

💡useRef hook

The useRef hook is a feature in React that allows access to a mutable ref object whose .current property is initialized as the argument passed to useRef. In the video, the useRef hook was explained in the previous episode, indicating the progressive nature of the series.

💡Functional components

Functional components in React are a simpler form of components that do not maintain state and are written in plain JavaScript functions. They receive props as their arguments and return React elements. The video script mentions creating two functional components, 'parent' and 'child', to demonstrate component communication.

💡Props

Props are a way to pass data from a parent component to a child component in React. They are read-only and should not be modified by the child component. The script explains how to pass the state of a parent component to a child component via props, which is a fundamental concept in React for component communication.

💡State

State in React is an object that holds information that may change over time. It is used to record and react to user interactions, data fetching, etc. The script describes how to create and update state in a parent component, which is then passed to a child component.

💡Callback function

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some action. In the video, the concept is used to show how a parent component can pass a function to a child component, which the child can then execute.

💡useEffect hook

The useEffect hook in React is used to perform side effects in function components. It is similar to componentDidMount, componentDidUpdate, and componentWillUnmount in class components. The script uses useEffect to demonstrate how a child component can react to changes in props, which triggers the execution of a function.

💡Context

Context provides a way to pass data through the component tree without having to pass props down manually at every level. It is mentioned at the end of the script as a solution to the problem of 'props drilling', where data needs to be passed through many layers of components.

💡Props drilling

Props drilling refers to the process of passing props through many levels of nested components, which can become complex and hard to manage. The video script uses this term to describe a scenario where communication between deeply nested components is required, and how context can help overcome this challenge.

💡Sibling components

In React, sibling components are components that share the same parent. The script mentions that communication between siblings can be indirect and requires passing data through their common parent, which is a common challenge in component architecture.

Highlights

Introduction to React JS Zero to Hero series for beginners

Explanation of useRef hook from the previous video

Introduction to communication between components in React

Creation of a new React application with parent and child components

Demonstration of passing state from parent to child component

Explanation of passing parent state as a prop to child

Showcasing state update in child component when parent changes

Reverse scenario: passing child component state to parent

Maintaining state in parent component for child's input

Using callback function to pass state from child to parent

Example of invoking parent function from child component

Exploring indirect communication between siblings through parent

Introduction to the concept of props drilling

Discussing the complexity of props drilling in deep component trees

Teasing the topic of context to overcome props drilling in the next video

Assignment task involving communication between two child components via a parent

Providing a solution code repository link for the assignment

Encouragement for viewers to like, subscribe, and support the channel

Transcripts

Hi Friends

Welcome back to React JS - Zero to Hero series.

This series is for beginners who wants to learn React JS from Scratch.

In the last video I have explained about useRef hook.

In this video I am going to explain about communication between components.

Let's start.

To explain this I have created a new react application in which I have created two functional

components, parent and child.

In app component, I am using parent component and in parent component I am using the child

component and so we can see this.

In parent component, let me create a text box.

Let me also create a state and let me update this state with the text

box value.

My requirement is I need to show this text box value in the child component.

This requirement is straight forward.

I can pass this parent state as a prop to child and in the child component, I can show

this prop.

And so, we can see this and when I change this in parent we can see the value in the

child is getting changed.

Now, let me try the reverse.

Let me have the text box in the child component.

Now, I need to show this text box value in the parent component.

In the earlier requirement, as we can access the child component from the parent component,

we were able to pass it as props and we achieved that easily.

But in child component, we don't have direct access to parent component.

So how can we do this.

To achieve this requirement, we should not maintain the state in the child component,

we need to maintain in the parent component.

So, let me move this to parent component and let me show this state here.

And, we can pass this setChildInput function as a callback function through prop to child

component.

And in child component, we can access this function through props.

Like this.

Now we can see, when we change something in this text box, it is getting changed in the

parent component.

Ok, let's see this scenario.

Let me create a function in the parent component.

And let me create a button in the child component.

My requirement is when I click this button in the child component, this function in the

parent component should be invoked.

We can follow the same callback approach and achieve it easily.

Let me pass this function to child through props as a callback function.

And in child component, onClick of this button, let me call props dot this one.

And so, when I click this button in the child, we can see the function in the parent is called.

Now, let's try the reverse.

Let me create the button in the parent and let me have the function in the child.

On clicking this button in the parent, we need to call the function in the child.

This is not going to be a straight forward approach.

We can achieve this in different ways.

Let me show you one way.

A function can be called in different ways.

Either through an event like onClick, onChange, etc or when the component is getting loaded

or rerendered.

For our requirement, we can call the function when the component is rerendered.

And, we know a component in react can be rerendered when there is a change in state or props.

So, first let me introduce an useEffect in child component and let me call this child

function inside this useEffect.

In dependency array, let me give a props.

So when this props is changed, this function will be invoked.

Now, in the parent component, I can find a way to change this props.

I can maintain a state and I can change this state on clicking this button.

And, I can pass this state as props to the child component.

And so, when this button in the parent is clicked this props will be changed and so

this will trigger the useEffect in the child and so the function in the child is called.

Ok.

I hope you understood how we can communicate from parent component to child component and

vice versa.

This way of communicating through props will be helpful when the components are closely

related.

Sometimes, we may need to communicate between siblings.

By this props approach we can communicate indirectly through parent.

For example, if we need to communicate from child one to child two, first we need to communicate

from child one to parent and then from parent to child Two.

This becomes complex when the level of child and parent components increase.

Assume this situation.

Now, if we need to communicate from this component to this component, first we need to communicate

all the way up to parent and from there we need to communicate all the way down to this

child.

This is difficult.

This is called props drilling.

To overcome this difficulty, we have context.

That is what I am going to explain in the next video.

Ok.

Let me give you a task in this topic.

You can create an application like this.

In which I have created two child components and a parent component.

When this button in the child one component is clicked, you need to change the color of

this div in the child two component and when you type something in this text box in the

child two component, that should be reflected in the child one component.

Try this, if you need the solution code, you can get it from this repo.

The link is also available in the description.

That's all for today.

Please like this video.

Subscribe to my channel and support me.

Thank you.

Bye.