Props & State in React Native

Props

Props is short for “properties”. Props let you customize React components. For example, here you pass each <Cat> a different name for Cat to render:

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

const Cat = (props) => {
  return (
    <View>
      <Text>Hello, I am {props.name}!</Text>
    </View>
  );
}

const Cafe = () => {
  return (
    <View>
      <Cat name="Maru" />
      <Cat name="Jellylorum" />
      <Cat name="Spot" />
    </View>
  );
}

export default Cafe;

State

Functional Component

import React, { useState } from "react";
import { Button, Text, View } from "react-native";

const Cat = (props) => {
  const [isHungry, setIsHungry] = useState(true);

  return (
    <View>
      <Text>
        I am {props.name}, and I am {isHungry ? "hungry" : "full"}!
      </Text>
      <Button
        onPress={() => {
          setIsHungry(false);
        }}
        disabled={!isHungry}
        title={isHungry ? "Pour me some milk, please!" : "Thank you!"}
      />
    </View>
  );
}

const Cafe = () => {
  return (
    <>
      <Cat name="Munkustrap" />
      <Cat name="Spot" />
    </>
  );
}

export default Cafe;

State and Class Component

In class component state is stored as an Object.

import React, { Component } from "react";
import { Button, Text, View } from "react-native";

class Cat extends Component {
  state = { isHungry: true };

  render() {
    return (
      <View>
        <Text>
          I am {this.props.name}, and I am
          {this.state.isHungry ? " hungry" : " full"}!
        </Text>
        <Button
          onPress={() => {
            this.setState({ isHungry: false });
          }}
          disabled={!this.state.isHungry}
          title={
            this.state.isHungry ? "Pour me some milk, please!" : "Thank you!"
          }
        />
      </View>
    );
  }
}

class Cafe extends Component {
  render() {
    return (
      <>
        <Cat name="Munkustrap" />
        <Cat name="Spot" />
      </>
    );
  }
}

export default Cafe;