Set up Amplify GraphQL API

The Amplify API category provides an interface for retrieving and persisting your model data. The API category comes with default built-in support for AWS AppSync. The Amplify CLI allows you to define your API and provision a GraphQL service with CRUD operations and real-time functionality.

Goal

To setup and configure your application with Amplify API to save items in the backend.

Prerequisites

• An iOS application targeting at least iOS 11.0 with Amplify libraries integrated
  • For a full example of please follow the project setup walkthrough

Configure API

To start provisioning API resources in the backend, go to your project directory and execute the command:

amplify add api

Enter the following when prompted:

? Please select from one of the below mentioned services:
    `GraphQL`
# The part below will show you some options you can change, if you wish to change any of them you can navigate with
# your arrow keys and update any field, otherwise you can click on `Continue` to move on
? Here is the GraphQL API that we will create. Select a setting to edit or continue
    `Continue`
? Choose a schema template:
    `Single object with fields (e.g., “Todo” with ID, name, description)`
? Do you want to edit the schema now?
    `No`

The guided schema creation will output amplify/backend/api/{api_name}/schema.graphql containing the following:

type Todo @model {
  id: ID!
  name: String!
  description: String
}

To push your changes to the cloud, execute the command:

amplify push

Upon completion, amplifyconfiguration.json will be updated to reference provisioned backend resources. Note that this file should already be a part of your project if you followed the Project setup walkthrough.

Generate Todo Model class

To generate the Todo model, change directories to your project folder and execute the command:

amplify codegen models

The generated files will be under the amplify/generated/models directory. It is strongly advised not to put any hand written code in amplify/generated directory as it gets re-generated each time codegen is run.

AmplifyModels.swift
Todo.swift
Todo+Schema.swift

Drag and place the entire models directory into Xcode to add them to your project.

Install Amplify Libraries

target 'MyAmplifyApp' do
  use_frameworks!
  pod 'Amplify'
  pod 'AmplifyPlugins/AWSAPIPlugin'
end

pod install --repo-update

xed .

Initialize Amplify API

To initialize the Amplify API category, you are required to use the Amplify.add() method for the plugin followed by calling Amplify.configure().

Add the following imports to the top of your AppDelegate.swift file:

import Amplify
import AWSAPIPlugin

import Amplify
import AmplifyPlugins

Add the following code

class AppDelegate: NSObject, UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {

        do {
            try Amplify.add(plugin: AWSAPIPlugin(modelRegistration: AmplifyModels()))
            try Amplify.configure()
            print("Amplify configured with API plugin")
        } catch {
            print("Failed to initialize Amplify with \(error)")
        }

        return true
    }
}

@main
struct MyAmplifyApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {

    do {
        try Amplify.add(plugin: AWSAPIPlugin(modelRegistration: AmplifyModels()))
        try Amplify.configure()
        print("Amplify configured with API plugin")
    } catch {
        print("Failed to initialize Amplify with \(error)")
    }

    return true
}

Upon building and running this application you should see the following in your console window:

Amplify configured with API plugin

Create a Todo

func createTodo() {
    let todo = Todo(name: "my first todo", description: "todo description")
    Amplify.API.mutate(request: .create(todo)) { event in
        switch event {
        case .success(let result):
            switch result {
            case .success(let todo):
                print("Successfully created the todo: \(todo)")
            case .failure(let graphQLError):
                print("Failed to create graphql \(graphQLError)")
            }
        case .failure(let apiError):
            print("Failed to create a todo", apiError)
        }
    }
}

import Combine

func createTodo() -> AnyCancellable {
    let todo = Todo(name: "my first todo", description: "todo description")
    let sink = Amplify.API.mutate(request: .create(todo))
        .resultPublisher
        .sink { completion in
        if case let .failure(error) = completion {
            print("Failed to create graphql \(error)")
        }
    }
    receiveValue: { result in
        switch result {
        case .success(let todo):
            print("Successfully created the todo: \(todo)")
        case .failure(let graphQLError):
            print("Could not decode result: \(graphQLError)")
        }
    }
    return sink
}

Upon successfully executing this code, you should see an instance of todo persisted in your dynamoDB table.

To navigate to your backend, run amplify console api and choose GraphQL. This will open the AppSync console to your GraphQL service. Select Data Sources and select the Resource link in your TodoTable to bring you to the DynamoDB Console. Select the items tab to see the Todo object that has been persisted in your database.

Next steps

Congratulations! You've created a Todo object in your database. Check out the following links to see other Amplify API use cases:

• Fetch data
• Update data
• Subscribe to data
• Concepts
• Configure authorization modes