React Native - Props


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In our last chapter, we showed you how to use mutable state. In this chapter, we will show you how to combine the state and the props.

Presentational components should get all data by passing props. Only container components should have state.

Container Component

We will now understand what a container component is and also how it works.

Theory

Now we will update our container component. This component will handle the state and pass the props to the presentational component.

Container component is only used for handling state. All functionality related to view(styling etc.) will be handled in the presentational component.

Example

If we want to use example from the last chapter we need to remove the Text element from the render function since this element is used for presenting text to the users. This should be inside the presentational component.

Let us review the code in the example given below. We will import the PresentationalComponent and pass it to the render function.

After we import the PresentationalComponent and pass it to the render function, we need to pass the props. We will pass the props by adding myText = {this.state.myText} and deleteText = {this.deleteText} to <PresentationalComponent>. Now, we will be able to access this inside the presentational component.

src/components/home/Home.js

import React, { Component } from 'react'
import { View } from 'react-native'
import PresentationalComponent from './PresentationalComponent'

class Home extends Component {
   state = {
      myState: 'Lorem ipsum dolor sit amet, consectetur adipisicing elit,
         sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
         Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi
         ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in
         voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur 
         sint occaecat cupidatat non proident, sunt in culpa qui officia 
         deserunt mollit anim id est laborum.'
   }
   updateState = () ⇒ {
      this.setState({ myState: 'The state is updated' })
   }
   render() {
      return (
         <View>
            <PresentationalComponent myState = {this.state.myState} updateState = 
               {this.updateState}/>
         </View>
      )
   }
}
export default Home

Presentational Component

We will now understand what a presentational component is and also how it works.

Theory

Presentational components should be used only for presenting view to the users. These components do not have state. They receive all data and functions as props.

The best practice is to use as much presentational components as possible.

Example

As we mentioned in our previous chapter, we are using the ES6 function syntax for presentational components.

Our component will receive props, return view elements, present text using {props.myText} and call the {props.deleteText} function when a user clicks on the text.

src/components/home/PresentationalComponent.js

import React, { Component } from 'react'
import { Text, View } from 'react-native'

const PresentationalComponent = (props) ⇒ {
   return (
      <View>
         <Text onPress = {props.updateState}>
            {props.myState}
         </Text>
      </View>
   )
}
export default PresentationalComponent

Now, we have the same functionality as in our State chapter. The only difference is that we refactored our code to the container and the presentational component.

You can run the app and see the text as in the following screenshot.

React Native Props

If you click on text, it will be removed from the screen.



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