A Guide to Run your React Native Apps with Typescript

Setting up the project

To set up the project, we will use Expo CLI, a command-line tool whose various use-cases involves setting up a React Native project.

The first step is to install Expo CLI. You can check if you have Expo CLI installed by running the following command from your terminal:

expo whoami

If you have it installed, the installed version will be logged on to your terminal. If you don't have it installed, run the following command:

npm install --global expo-cli

--global so as it can be used all across your operating system.

Navigate to a location you intend your project to reside and run the following command to bootstrap our React Native project with TypeScript:

expo init -t expo-template-blank-typescript react-native-blog-app

Our application will be bootstrapped from a blank typescript application template from the above command. After the process is done:

• Navigate to the project folder:

cd react-native-blog-app

• Run your project by using:

npm run android # for android
npm run ios # for ios

Scan the QR code logged on your terminal using the Expo Go application on your device. The application will automatically load from there.

Creating application components

Create a directory inside the project directory and name it components. Inside the components directory, create two files:

• Posts.tsx: For rendering multiple posts.
• Post.tsx: For rendering a single post.

Edit Posts.tsx with dummy text:

import {Text,View} from "react-native";
export default function Posts(){
    return(
        <View>
            <Text>Posts content will be here</Text>
        </View>
    )
}

Edit Post.tsx with dummy text:

import {Text,View} from "react-native";
export default function Post(){
    return(
        <View>
            <Text>Post content will be here</Text>
        </View>
    )
}

In App.tsx, import the Posts component:

import Posts from './components/Posts';

Call the Posts component:

export default function App() {
  return (
    <View style={styles.container}>
      <Posts />
      <StatusBar style="auto" />
    </View>
  );
}

Adding posts

In this article, we will use static posts sourced inside the application. Create a lib directory inside the project folder. Inside lib, create a posts.ts file to host the posts. Edit posts.ts as follows:

export default [
    {
        id: 1,
        title: 'First Post',
        excerpt: 'This is the first post,
        content: 'But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure? On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee.'
    },
    {
        id: 2,
        title: 'Second Post',
        excerpt: 'This is the second post,
        content: 'But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure? On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee.'
    },
    {
        id: 3,
        title: 'Third Post',
        excerpt: 'This is the third post,
        content: 'But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure? On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee.'
    },
    {
        id: 4,
        title: 'Fourth Post',
        excerpt: 'This is the fourth post,
        content: 'But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure? On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee.'
    },
    {
        id: 5,
        title: 'Fifth Post',
        excerpt: 'This is the fifth post,
        content: 'But I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system, and expound the actual teachings of the great explorer of the truth, the master-builder of human happiness. No one rejects, dislikes, or avoids pleasure itself, because it is pleasure, but because those who do not know how to pursue pleasure rationally encounter consequences that are extremely painful. Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure? On the other hand, we denounce with righteous indignation and dislike men who are so beguiled and demoralized by the charms of pleasure of the moment, so blinded by desire, that they cannot foresee.'
    }
]

From above, we are exporting an array of posts. Each post has the following data:

• id: A unique integer value.
• title: The posts title.
• excerpt: Small description of the title.
• content: Dummy article content.

Fetching posts

To implement the functionality of fetching the posts, we will work on components/Posts.tsx.

• Import StyleSheet and the dummy posts:

import {StyleSheet} from 'react-native';
import posts from '../lib/posts';

• Define a post's structure:

interface Post {
    id: number;
    title: string;
    excerpt: string;
    content: string;
}

• Map the posts to the view:

export default function Posts(){
    return(
        <View>
            {
                posts.map((post:Post)=>{
                    return (
                        <View key={post.id} style={styles.postCard}> 
                            <Text style={styles.postTitle}>{post.title}</Text>
                            <Text style={styles.postExcerpt}>{post.excerpt}</Text>
                        </View>
                    )
            })}
        </View>
    )
}

• Append the styles:

const styles = StyleSheet.create({
    postCard:{
        width:'100%',
        padding:10,
    },
    postTitle:{
        fontSize:18,
        fontWeight:'bold',
    },
    postExcerpt:{
        fontSize:15,
        color:'#666',
    }
});

In App.tsx, edit the styles as follows, removing the center alignment:

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    paddingTop: 40,
  },
});

Conclusion

This guide walked you through a reflective introduction to Typescript and React Native. For better understanding, we have created a whole application that uses React Native to run the Typescript code.