Definition

Apollo Client is a GraphQL client library for iOS that enables executing GraphQL operations and mapping responses to strongly typed Swift models.

Core Concept

Apollo acts as the bridge between the iOS app and a GraphQL server by:

• sending queries and mutations
• parsing responses
• generating type-safe Swift models from .graphql files

Key Components

• ApolloClient

  Main entry point for executing GraphQL operations

• Generated Models

  Swift types generated from .graphql queries

• Network Transport

  Handles HTTP requests to the GraphQL endpoint

• Apollo Store (optional)

  Provides caching and normalized data storage

Basic Setup

import Apollo

let apollo = ApolloClient(url: URL(string: "<https://countries.trevorblades.com/>")!)

Executing a Query

apollo.fetch(query: GetCountriesQuery()) { result in
    switch result {
    case .success(let graphQLResult):
        print(graphQLResult.data?.countries)
    case .failure(let error):
        print(error)
    }
}