Keeping the application logic isolated in one place is really crucial, as this provides us with a single source of truth that can be referred to for any changes.
Using the container/presentational paradigm in React is one strategy to ensure the separation of concerns. We may distinguish between the application logic and the view by employing this pattern.
This pattern is an alternative to the higher-order component pattern in React.
Containers are components that isolate the application logic, restricting their concerns about what data has to be shown. while presentation components focus on how the data has to be shown.
Let us understand this by creating a component that shows a list of beers. We will create two components that will have their share of concerns.
Beer.js, a container component
This is a container component that will contain the application logic to fetch the beer list through an API and store the data in the local state.
Thes data will be then passed to the presentational component that will render the data.
This component doesn’t have to worry about the styling or layout because the presentational component will render the data.
import { useEffect, useState } from "react";
import BeerList from "./BeerList";
const Beer = () => {
const [beers, setBeers] = useState([]);
const fetchBeers = async () => {
try {
let response = await fetch(
"https://api.punkapi.com/v2/beers?page=1&per_page=10"
);
response = await response.json();
setBeers(response);
} catch (e) {
console.error("Error while fetching beers list", e);
}
};
useEffect(() => {
fetchBeers();
}, []);
return <BeerList beers={beers} />;
};
export default Beer;
BeerList.js, a presentational component
This is a presentational component that will receive the data as a prop and render it.
The complete focus of this component will be on the layout, styling, and rendering of the view.
Presentational components are pure components that do not mutate the input data; their sole focus is on rendering the data they have received, so they can also be reused.
import "./BeerList.css";
const BeerList = ({ beers }) => {
return beers.map((e) => (
<div key={e.id} className="wrapper">
<div className="hero-image">
<img src={e.image_url} alt={e.name} title={e.name} />
</div>
<div className="details">
<span>
<strong>Name</strong>: {e.name}
</span>
<span>
<strong>Tagline</strong>: {e.tagline}
</span>
<span>
<strong>First Brewed on</strong>: {e.first_brewed}
</span>
<p>
<strong>Description</strong>: {e.description}
</p>
</div>
</div>
));
};
export default BeerList;
Styling the presentational component
* {
box-sizing: border-box;
}
.wrapper {
display: flex;
align-items: center;
flex-wrap: wrap;
border: 1px solid #000;
margin-bottom: 10px;
box-shadow: 0 3px 3px rgba(0, 0, 0, 0.27);
padding: 10px;
}
.hero-image {
flex: 0 100px;
}
.hero-image > img {
width: 100px;
height: 200px;
}
.details {
padding: 20px;
flex: 1;
display: inline-flex;
align-items: center;
flex-wrap: wrap;
}
.details > span {
flex: 0 100%;
line-height: 30px;
}
Outcome of the container and presentational pattern
As the Beer.js is the container component, it composes the presentational component within, thus we can just render the Beer.js and it will render the view.
import { StrictMode } from "react";
import { createRoot } from "react-dom/client";
import Beer from "./Beer";
const rootElement = document.getElementById("root");
const root = createRoot(rootElement);
root.render(
<StrictMode>
<Beer />
</StrictMode>
);
Using a hook to replace the container component
As React has introduced hooks, we can replace the container component with the hooks, which will remove the need for nesting the components.
A custom hook can be created that will fetch the data.
import { useEffect, useState } from "react";
const useBeer = () => {
const [beer, setBeer] = useState([]);
useEffect(() => {
fetch("https://api.punkapi.com/v2/beers?page=1&per_page=10")
.then((res) => res.json())
.then((res) => setBeer(res));
}, []);
return beer;
};
export default useBeer;
And this hook can be directly used in the presentational component to render the data.
import "./BeerList.css";
import useBeer from "./useBeer";
const BeerList = () => {
const beers = useBeer();
return beers.map((e) => (
<div key={e.id} className="wrapper">
<div className="hero-image">
<img src={e.image_url} alt={e.name} title={e.name} />
</div>
<div className="details">
<span>
<strong>Name</strong>: {e.name}
</span>
<span>
<strong>Tagline</strong>: {e.tagline}
</span>
<span>
<strong>First Brewed on</strong>: {e.first_brewed}
</span>
<p>
<strong>Description</strong>: {e.description}
</p>
</div>
</div>
));
};
export default BeerList;
Hooks are an excellent addition to the React framework that really helps to isolate the application logic.
Outcome of the hook and presentational pattern
As the Beer.js is the container component, it composes the presentational component within, thus we can just render the Beer.js and it will render the view.
import { StrictMode } from "react";
import { createRoot } from "react-dom/client";
import BeerList from "./BeerList";
const rootElement = document.getElementById("root");
const root = createRoot(rootElement);
root.render(
<StrictMode>
<BeerList />
</StrictMode>
);
Conclusion
The contianer/presentational pattern in React is most suited for the class-based component where we cannot use the hooks.
The hook/view pattern is for the functional components in React.
Both are similar, as their focus is on separating the logics.
By separating the concerns, it makes the component more readable and developer-friendly. For example, as presentational components are pure components that do not mutate the application logic, they can be easily extended by developers. They don’t have to worry about the logic implications in case they change anything, as its sole purpose is to view things.
It also makes them easy to test, as we are sure that they will just render the data they will be receiving.
