GraphQL React Native: A Comprehensive Guide For Building Scalable Mobile Apps

GraphQL is a powerful tool for building client applications, especially when used in combination with React Native. GraphQL provides a flexible syntax and system for describing data requirements and interactions, allowing clients to use an API that provides exactly the data they need. Developing a strong type schema for your API is possible with GraphQL React Native.

It also ensures that the API resolves data and that client queries are checked against a schema defined on the server-end. GraphQL React Native has several specifications that make it a declarative query language, as opposed to an API that is statically typed (built around Typescript). This allows clients to benefit from those types of systems by asking the API for exactly the data they need.

GraphQL provides a user-friendly interface for product development and a powerful platform for tool-building. It also provides a runtime environment for fulfilling client queries with existing data and a complete and understandable description of the data in your API.

GraphQL offers clients the advantage of asking for exactly what they need, making it easier to evolve APIs over time, and enabling powerful developer tools. It simplifies the workflow of building a client app and removes the complexity of managing API endpoints in client-side apps by providing a single HTTP endpoint for fetching data.

Why Use GraphQL?

GraphQL is a revolutionary approach to building APIs that eliminates the problems of overfetching and underfetching associated with RESTful APIs. The traditional way of sending and fetching data over HTTP is through REST-based APIs, which have gained a high adoption rate in recent years. However, the fixed data structure returned by RESTful APIs can lead to overfetching or underfetching of data by the client.

Overfetching occurs when the client downloads more information than what is required by the app, while underfetching occurs when the client does not download enough information. GraphQL addresses these problems by providing a single endpoint that handles all client requests using GraphQL operations such as queries and mutations.

This allows clients to customize their requests and ask for multiple resources or fields in the same request, giving them control over the data they fetch. In this way, overfetching and underfetching can be avoided. Additionally, GraphQL allows for a separation between the client and server, meaning that once the server is ready, the client can make requests as needed without affecting each other.

The following example will clarify how flexible APIs can be built for your application using GraphQL over RESTful API.

The above example shows the overfetching problem associated with rest API. For example, if an app requires only the id and first name of the user, but API will return all the user’s information that is not needed, this problem is known as an overfetching problem. The following example in the picture demonstrates how this overfetching problem is overcome in GraphQL.

The above example in the picture shows how only the required information, i.e., the id and the first name returned by the query in GraphQL, overcomes the problem of overfetching with REST API.

The above example shows an overfetching problem with the rest API. For example, if an application requires a user’s email and quotes from the user, then two API calls are made, one to get email by user id and the other sections by user id. This kind of problem is known as underfetching. The following example in the picture demonstrates how this overfetching problem is overcome in GraphQL.

The above example shows how a query is designed to get the user’s email and quotes. Here a nested question is added to get quotes from that user. But all the information returns in a single query call itself. This is how overfetching problem has been solved using GraphQL.

Benefits Of GraphQL

Ask for exactly what you need: By sending a GraphQL query to your API, you will get exactly what you need based on the requested question. GraphQL query always return predictable results as it returns response JSON based on what resources and fields are mentioned in the query. As the application has full control over the data they want, no server is responsible for that, so it looks stable and works faster.

Example: The following example demonstrates how a GraphQL request will return the user’s name whose id is 4.

The above query will return the resulting data (in JSON) as below:

Get many resources in response to a single request: The returned Body of GraphQL queries consists of only fields or combinations of many resources along with their references.

While using apps with REST APIs requires loading from multiple URL API calls, whereas GraphQL API’s query will only return all the data the app needs in a single request. If applications using GraphQL can also be even quicker on slow mobile network connections.

Introduction To Apollo Client

Apollo Client is a JavaScript library for state management that allows managing both local and remote data using GraphQL. It helps to fetch data from the server, cache it into the application, and modify server data. Apollo Client is a GraphQL client for

JavaScript and native platforms that offers a robust state-management tool and a zero-config caching system. It has a declarative approach to fetching data, making it easy to implement pagination using GraphQL. Additionally, it offers an Optimistic UI for client-side applications. Apollo has an inbuilt ecosystem for GraphQL applications and can be used to develop both client-side and server-side apps separately.

Steps To Integrate Apollo Client In React Native Applications

Step 1: Applications that use Apollo Client require to install following two top-level dependencies:

@apollo/client: This package contains everything required to set up Apollo Client. It also includes the in-memory cache for enabling caching mechanism, local state management, and error handling mechanism.

graphql: This package provides logic for implementing GraphQL React Native queries and mutation.

We can run the following command to install both packages mentioned above npm install @apollo/client graphql

Step 2: Initialize the Apollo client: Once all the above packages are installed, we can now initialize the instance of the Apollo client as below:

In index.js, let’s first import the ApolloClient from @apollo/client package as below:

Ex: index.js:

Next, Initialize ApolloClient by passing uri and cache fields to its constructor, which is a configuration object:

Ex: index.js:

In the above example,
uri: Its nothing but the base URL of our GraphQL server
Cache: It specifies an instance of InMemoryCache, which the Apollo client uses to cache the result of queries after fetching them

Step 3: Now we can connect your client to React application: The apolloProvider component can connect Apollo Client to React application. It wraps your React Application and places Apollo Client context, allowing access to it from anywhere within the component tree added.

You can see the below example. 

Step 4: Connect the Apollo client to React application. Now we can connect the Apollo client to the React application using the ApolloProvider component. Apollo provider wraps React parent component of the tree and places the Apollo client on the context. So it’s accessible anywhere within the component tree added.

The example demonstrated how React app’s parent component wrapped with the Apollo provider. So that React components can access GraphQL data.

Now Our client is ready to start fetching and modifying server data.

Official documentation for setup: Click here

GraphQL Basics

Operations in GraphQL are actions performed on the server. The main types of operations in GraphQL are:

Query: To fetch and read server data, Query operations can be implemented. This is a read-only fetch operation. The main hook used to execute queries in GraphQL is the useQuery hook.

useQuery: This is a React hook used in the Apollo app to execute queries. It can be called by passing a GraphQL query string, and it returns a JSON object containing the data, loading, and error properties.

The below example demonstrates how we can write queries in graphQL. GET_POSTS is the name given to GraphQL query and Query string wrapped in gql function to parse them into a query document.

Example:

Next, we’ll create a component named posts. Inside it, we’ll pass our GET_POSTS query to the useQuery hook:

Mutation: To create, update, and delete data on a server, Mutation operations can be implemented. This is known as a CUD (create, update, delete) operation. The main hook used to send updates to your GraphQL server is the useMutation hook.

useMutation: This is a React hook that is primarily used for executing mutations. It can be called by passing a GraphQL mutation string, and it returns an object that can be used to perform the mutation.

Example:

Let’s say we’re creating a post list application, and we want the user to be able to post items to their list. First, we’ll create a corresponding GraphQL mutation named CRAETE_POST. GraphQL string that defines mutation needs to be wrapped in a gql function to parse them into a query document.

Next, we’ll create a component named AddPost to upload the post created. Inside it, we’ll pass our CRAETE_POST mutation to the useMutation hook:

Subscriptions: This is one of the operations in GraphQL. When a specific event occurs, it sends data from the server to its client. Subscription operation usually implemented with Websocket, mostly for chat application.

When working with GraphQL, you will primarily deal with queries and mutations. These operations have unique names assigned to them on the client side.

Operations can also define arguments, similar to how a function in most programming languages works. Queries and mutations in GraphQL React Native can be specified by passing arguments or variables. These values must be provided at runtime during the execution of the operations described in the document.

The following diagram illustrates some conventions used on the client side when implementing GraphQL. Aliasing is important to avoid conflicts with field names.

It’s worth mentioning that the diagram you are referring to is not provided so it’s hard to understand the context but overall the information provided is clear and accurate.