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If you’re using React or React Native, then you’re probably familiar with its component-based structure and the way it handles state. But did you know that React Native also has a number of hooks built in? These hooks let you tap into the react native lifecycle at different points, which can be useful for performing tasks such as data loading or saving. In this blog post, we’ll take a look at how to use react native lifecycle hooks effectively in your own projects.
So what exactly are react native lifecycle hooks? Let’s take a look.
React native lifecycle hooks:
React native lifecycle hooks are essentially functions that let you tap into the react native component lifecycle at specific points. Hooks are a new addition to React 16.8. There are a number of different hooks available, each of which is designed for a different purpose.
For example, there’s the useEffect hook, which lets you perform side effects such as data fetching or saving. There’s also the useLayoutEffect hook, which lets you run code before react has a chance to update the DOM. And there are many others.
The react native component lifecycle is divided into a number of different phases, each of which has its own lifecycle hooks. The most important phase for our purposes is the render phase, which is where react actually updates the DOM. Other important phases include the mount and unmount phases, which correspond to when a component is added to or removed from the DOM.
Using the State Hook:
One of the most common uses for react native lifecycle hooks is to manage the state. The useState hook lets you create variables that hold react states. You can then use these variables in your components to render dynamic content.
To use the useState hook, you first need to import it from react:
import React, { useState } from 'react';You can then create a state variable by calling the useState function:
const [myState, setMyState] = useState(initialValue);The useState function takes an initial value for the state variable, which can be any type of value (including objects and arrays). The initial value is only used when the component is first mounted.
Once you’ve created a state variable, you can access its value via the myState variable, and you can update its value by calling the setMyState function.
Here’s an example of how to use the useState hook to create a counter component:
import React, { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
// ...
);
}In this example, we’ve created a state variable called count, which is initialized to 0. We can then increment or decrement the count by calling the setCount function.
You can also use the useState hook to create more than one state variable. Just call the useState function multiple times:
const [myFirstState, setMyFirstState] = useState(initialValue);
const [mySecondState, setMySecondState] = useState(initialValue);This is often useful for storing different pieces of state that are independent of each other.
Using the Effect Hook:
The useEffect hook lets you perform side effects in react components. Side effects are operations that don’t directly affect the component, but which need to be run when something changes.
Data fetching is a common use case for the useEffect hook. For example, you might want to fetch data from an API when a component mounts, or when a particular state variable changes.
To use the useEffect hook, you first need to import it from react:
import React, { useEffect } from 'react';You can then define an effect by passing a function to the useEffect hook:
useEffect(() => {
// ...
});The function you pass to the useEffect hook will run after the component has been rendered.
If you want the effect to run only when a particular state variable change, you can pass that variable as a second argument to the useEffect hook:
useEffect(() => {
// ...
}, [stateVariable]);In this example, the effect will only run when the stateVariable changes.
You can also define multiple effects by passing an array of functions to the useEffect hook:
useEffect(() => {
// ...
}, []);This example defines two effects: one that runs when the component mounts, and one that runs when the stateVariable changes.
Wrapping Up:
React native lifecycle hooks are a powerful way to manage state and side effects in react components. The useState and useEffect hooks let you create variables and perform side effects, respectively.
When used effectively, react native lifecycle hooks can make your components more flexible and easier to maintain. So don’t be afraid to use them in your own react projects!
* * * *
Rules of Hooks:
There are a few rules that you need to follow when using hooks.
First, hooks can only be called from react function components or custom Hooks. They can’t be called from regular JavaScript functions.
Second, hooks should only be called at the top level of a react function component. Don’t call Hooks inside loops, conditions, or nested functions.
Basic Hooks:
Now let’s take a look at some of the most commonly used react native lifecycle hooks.
useState:
The useState hook is used to add state to a react component. It takes a single argument, which is the initial state of the component. The useState hook returns a pair of values, the first of which is the current state of the component, and the second of which is a function that can be used to update the state.
const [state, setState] = useState(initialState);useEffect:
The useEffect hook is used to perform side effects such as data fetching or saving. It takes a function as its only argument, and this function is called whenever the component is rendered.
useEffect(() => {
// Perform side effects here
const subscription = props.source.subscribe();
return () => {
// Clean up the subscription
subscription.unsubscribe();
};
}, []);useContext:
The useContext hook is used to access react context. It takes a Context object as its only argument, and it returns the current context value for that Context object.
const context = useContext(MyContext);Additional Hooks:
useReducer:
The useReducer hook is used to update state in a react component. It takes two arguments, the first of which is a reducer function and the second of which is initial state. The useReducer hook returns the current state of the component and a dispatch function that can be used to update the state.
const [state, dispatch] = useReducer(reducer, initialState);useCallback:
The useCallback hook is used to memoize a function. It takes a function as its first argument and an array of dependencies as its second argument. The useCallback hook returns a memoized version of the function that is only re-created if one of the dependencies has changed.
const memoizedCallback = useCallback(
() => {
doSomething();
},
[dependency]
);useMemo:
The useMemo hook is used to memoize a value. It takes a function as its first argument and an array of dependencies as its second argument. The useMemo hook returns the memoized value, which is only recalculated if one of the dependencies has changed.
const memoizedValue = useMemo(() => calculateValue(), [dependency]);useRef:
The useRef hook is used to create a ref object. It takes an initial value as its only argument. The useRef hook returns a mutable ref object whose current property is initialized to the initial value.
const ref = useRef(initialValue);useImperativeHandle:
The useImperativeHandle hook is used to give a react component the ability to control its own DOM. It takes a function as its first argument and an array of dependencies as its second argument. The useImperativeHandle hook returns a ref object whose current property is initialized to the initial value.
const ref = useImperativeHandle(() => ({
focus: () => {
// Do something with the DOM here
}
}), []);useLayoutEffect:
The useLayoutEffect hook is used to run code before react has a chance to update the DOM. It takes a function as its only argument, and this function is called synchronously after the component is rendered.
useLayoutEffect(() => {
// Run code here
}, []);useDebugValue:
The useDebugValue hook is used to display a custom label for a react component in the react devtools. It takes a value as its only argument.
useDebugValue(value);useTransition:
The useTransition hook is used to perform animations when a react component is mounted or unmounted. It takes an animation function as its first argument and a config object as its second argument. The useTransition hook returns a tuple containing an animation style object and a boolean value indicating whether the component is mounted.
const [animationStyle, isMounted] = useTransition(() => ({
// Animate here
}), {
// Config here
});useId:
The useId hook is used to generate a unique id for a react component. It takes an optional prefix string as its only argument. The useId hook returns a string that is unique to the component.
const id = useId("prefix");Library Hooks:
useSyncExternalStore:
The useSyncExternalStore hook is used to sync a react component’s state with an external store. It takes the external store as its first argument and an options object as its second argument. The useSyncExternalStore hook returns the current state of the react component.
const state = useSyncExternalStore(externalStore, {
// Options here
});useInsertionEffect:
The useInsertionEffect hook is used to run code when a react component is inserted into the DOM. It takes a function as its only argument, and this function is called when the component is inserted into the DOM.
useInsertionEffect(() => {
// Run code here
});So how can you use react native lifecycle hooks effectively in your own projects?
Let’s take a look at a few examples.
If you need to perform a side effect such as data fetching or saving, then the useEffect hook is the one you want to use. This hook lets you run code after react has updated the DOM, which means that it’s a good place to perform tasks that need access to the DOM.
If you need to run code before react has a chance to update the DOM, then you can use the useLayoutEffect hook. This is useful for tasks such as measuring the size of a component or setting up a subscription.
Conclusion:
And there are many other react native lifecycle hooks that you can use for different purposes. So experiment and see what works best for your project.
Do you have any tips for using react native lifecycle hooks effectively? Let us know in the comments.
