How to build a real-time todo app with React Native

Thanks to Bela Bordeaux

A todo app touches on all the important parts of building any data-driven app, including the Create, Read, Update and Delete (CRUD) operations. In this story I’ll be building a todo app with one of the most popular mobile frameworks, React Native.

I’ll be using ReactiveSearch Native, an open-source library which provides React Native UI components and simplifies building data-driven apps.

Here’s what I’ll be building in this story:

Todo App

Check out the app on snack or on expo.

What is React Native?

Here’s what the docs say:

React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.

Even if you’re just getting started with React or React Native, you should be able to follow along with this story and build your very own real-time todo app.

Why use ReactiveSearch? ⚛

ReactiveSearch is an open-source React and React Native UI components library for Elasticsearch which I’ve co-authored with some awesome people. It provides a variety of React Native components that can connect to any Elasticsearch cluster.

I’ve written another story on Building a GitHub Repo Explorer with React and Elasticsearch which you may check out for a brief overview of Elasticsearch. Even if you’ve had no experience with Elasticsearch you should be able to follow along with this story fine.

Setting things up ⚒

We will be using the React Native version of the library here.

Before we start building the UI, we’ll need to create a datastore in Elasticsearch. ReactiveSearch works with any Elasticsearch index and you can easily use it with your own dataset.

View my app dataset here. You can also clone this to your own app

For brevity, you can use my dataset directly or create one for yourself using appbase.io which lets you create a hosted Elasticsearch index (aka app).

All the todos are structured in the following format:

{
  "title": "react-native",
  "completed": true,
  "createdAt": 1518449005768
}

The starter project

Before we get started, I would recommend installing yarn. On Linux it can be done simply by adding the yarn repository and running the install command via your package manager. On Mac, you should install Homebrew first to make things simpler. Here are the yarn installation docs for more detail. The next thing which you may install is watchman. Its a file watching service which will help the react-native packager to run smoothly.

I’ve setup the starter project with create-react-native-app in a GitHub branch here. You may download a zip or clone the base branch by running the following command: 😌

git clone -b base https://github.com/appbaseio-apps/todos-native

• Next install the dependencies and start the packager:

cd todos-native && yarn && yarn start

• After the packager starts, you may run the app on your phone using the Expo app or using an Android or IOS emulator:

Base setup with all tabs. Clone from here.

Diving into code 🏊

Once you have cloned the code from the base branch, you should see a directory structure like below:

navigation
├── RootComponent.js         // Root component for our app
├── MainTabNavigator.js      // Tab navigation component      
screens
├── TodosScreen.js           // Renders the TodosContainer    
components        
├── Header.js                // Header component         
├── AddTodo.js               // Add todo input        
├── AddTodoButton.js         // Add todo floating button        
├── TodoItem.js              // The todo item         
├── TodosContainer.js        // Todos main container
api                          
├── todos.js                 // APIs for performing writes
constants                    // All types of constants used in app
types                        // Todo type to be used with prop-types
utils                        // Streaming logic goes here

Let’s breakdown what the base setup comes with:

1. Navigation

• All the necessary configurations for connecting to Elasticsearch are at constants/Config.js.
• We’re using TabNavigator from react-navigation for showing the All, Active and Completed todos screen. This is rendered by the navigation/RootComponent.js. You’ll notice the RootComponent wraps everything inside the ReactiveBase component from ReactiveSearch. This component provides all the necessary data to the child ReactiveSearch components. You can connect your own Elasticsearch index here by just updating the configurations in constants/Config.js.

The navigation logic is present in navigation/MainNavigator.js. Lets go over how it works. Here are the docs for tab navigation if you wish to reference anything.

Main tab navigation logic. Already present in the starter project

• The TabNavigator function accepts two arguments, the first being the route configurations and the second being the TabNavigator configurations. In the above snippet, we’re passing the configurations for showing a tab navigation bar at the bottom and setting different icons for each tab.

2. TodosScreen and TodosContainer

The TodosScreen component in screens/TodosScreen.js wraps our main TodosContainer component in components/TodosContainer.js where we’ll be adding various components for the app. The TodosContainer will show filtered data, based on whether we’re on the All, Active, or Completed tab.

3. APIs for Creating, Updating and Deleting todos

The APIs for CUD operations on Elasticsearch are present in api/todos.js . It contains three simple methods add, update and destroy which work with any Elasticsearch index as specified in constants/Config.js. An important point to keep in mind is that each todo item we create will have a unique _id field. We can use this _id field for updating or deleting an existing todo.

For our app, we’ll just need three methods for adding, creating or deleting todos. However, you can find a detailed explanation about the API methods at the docs.

Building the components and UI 💻

Lets start adding some components to complete the functionality of the app.

1. Adding Todos

We’ll use Fab from native-base to render a floating button for adding todos.

Adding the floating button for adding todos

Now you can use this component in components/TodosContainer.js.

import AddTodoButton from './AddTodoButton';
...
export default class TodosContainer extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        ...
        <AddTodoButton />
      </View>
    );
  }
}

Once we’ve added the button, we’ll see something like this:

After adding the AddTodoButton

Now, when someones clicks on this button, we’ll need to show the input for adding a todo. Lets add the code for this in components/AddTodo.js.

Component for add todo input

The main components used here are TextInput, Checkbox and Ionicons with straightforward props. We’re using title and completed from the state. We’ll be passing the props todo, onAdd, onCancelDelete and onBlur from the components/TodosContainer.js. These will help us in adding new todos or resetting the view if you wish to cancel adding todos.

Now we can update components/TodosContainer.js with the required changes for rendering AddTodo component:

The AddTodo component is rendered inside a ScrollView component. We also pass an onPress prop to the AddTodoButton to toggle the state and conditionally display the AddTodo component based on this.state.addingTodo. The onAdd prop passed to AddTodo also creates a new todo using the add API at api/todos.js.

After clicking the add button, we’ll see the input for adding a todo like this:

Adding a todo

2. Displaying Todos

After you finish adding a todo, it’s added into Elasticsearch (which we configured in constants/Config.js). All this data can be viewed in realtime by using ReactiveSearch Native components.

There are over 10 native UI components that the library provides. For our todo app, we will primarily utilize the ReactiveList component to show the state of todos.

Lets add the ReactiveList component and get our todos displaying. We’ll add this component in components/TodosContainer.js and the necessary methods for it to work. Here’s how the ReactiveList will be used:

Rendering the ReactiveList

We haven’t added the onAllData method yet, but let’s understand a bit about the props that we have used here:

• componentId — unique identifier for the component.
• defaultQuery: the query to be applied initially for the list. We’ll use match_all to show all the todos in default case.
• stream: whether to stream new result updates or just show historical results. By setting this to true, we now also listen for the live Todo updates. We’ll add the streaming related logic later.
• onAllData — a callback function which receives the list of current todo items and the streaming (new todos and any updates) and returns a React component or JSX to render. Here’s how the syntax looks like:

Read more about onAllData here.

You can read more about all of these props in detail on the ReactiveList’s docs page.

To see something, we’ll need to return a JSX or React component from onAllData callback. For this, we will use React Native’s FlatList which is composed of Text components. In the next step we’ll add our custom TodoItem component.

Adding the onAllData and filterTodosData methods

Integrating ReactiveList with onAllData

3. Adding TodoItem(s)

Next, we’ll create a separate component TodoItem for showing each todo which will contain all necessary markups for a todo item like the CheckBox, Text, and a delete Icon. This goes in components/TodoItem.js:

This component gets the todo from its props along with onDelete and onUpdate which are used to update and delete the todo item respectively. We’re using these at the necessary places using the onPress prop of the components we’re using.

Next, we can import and use the TodoItem component in our onAllData in components/TodosContainer.js. We’ll pass the todo as a prop along with the API methods for update and destroy which will be used by TodoItem component.

Using the TodoItem component in TodosContainer

After adding TodoItem in TodosContainer

4. Streaming Data Updates

You might have noticed that the todos are displaying fine, except you’re unable to view updated todos without refreshing the app. In this final step, we’re going to fit that missing part of the puzzle.

In the previous section, we added an onAllData method for the ReactiveList component. The second parameter of onAllData receives streaming updates which we’re going to utilize to always keep the todos updated. Here’s how the updated onAllData method will look like in components/TodosContainer.js.

Updating onAllData to stream updates

The mergeTodos method is present in utils/index.js. Here’s how it works:

Annotated code for merging streaming todos

The streamData receives an array of todo objects when they’re created, deleted, or updated. If an object is updated, it contains a _updated key set to true. Similarly, if an object is deleted, it contains a _deleted key set to true. If an object is created, it contains neither of the two. Using these points, we’ve added the mergeTodos function.

With this, you should be able to see the changes to todo items in realtime! If you have an additional device/emulator running the same app, both will stream new updates too. 😄

Useful links

1. Todos app demo, expo link, starter project and final source code
2. ReactiveSearch GitHub repo ⭐️
3. ReactiveSearch docs

Hope you enjoyed this story. If you have any thoughts or suggestions, please let me know and have fun!

Special thanks to Dhruvdutt Jadhav for helping me with this story and the Todos app. 🙌