Build API clients for Dart

In this tutorial, you build a sample app in Dart that calls a REST API that doesn't require authentication.

Required tools

• Dart SDK 3.6 or above

Create a project

Run the following commands in the directory where you want to create a new project.

dart create -t console cli

Add dependencies

Before you can compile and run the generated API client, you need to make sure the generated source files are part of a project with the required dependencies. Your project must have a reference to the bundle package. For more information about Kiota dependencies, see the dependencies documentation.

Run the following commands to get the required dependencies.

dart pub add microsoft_kiota_bundle

Generate the API client

Kiota generates API clients from OpenAPI documents. Create a file named posts-api.yml and add the following.

openapi: '3.0.2'
info:
 title: JSONPlaceholder
 version: '1.0'
servers:
 - url: https://jsonplaceholder.typicode.com/

components:
 schemas:
 post:
 type: object
 properties:
 userId:
 type: integer
 id:
 type: integer
 title:
 type: string
 body:
 type: string
 parameters:
 post-id:
 name: post-id
 in: path
 description: 'key: id of post'
 required: true
 style: simple
 schema:
 type: integer

paths:
 /posts:
 get:
 description: Get posts
 parameters:
 - name: userId
 in: query
 description: Filter results by user ID
 required: false
 style: form
 schema:
 type: integer
 maxItems: 1
 - name: title
 in: query
 description: Filter results by title
 required: false
 style: form
 schema:
 type: string
 maxItems: 1
 responses:
 '200':
 description: OK
 content:
 application/json:
 schema:
 type: array
 items:
 $ref: '#/components/schemas/post'
 post:
 description: 'Create post'
 requestBody:
 required: true
 content:
 application/json:
 schema:
 $ref: '#/components/schemas/post'
 responses:
 '201':
 description: Created
 content:
 application/json:
 schema:
 $ref: '#/components/schemas/post'
 /posts/{post-id}:
 get:
 description: 'Get post by ID'
 parameters:
 - $ref: '#/components/parameters/post-id'
 responses:
 '200':
 description: OK
 content:
 application/json:
 schema:
 $ref: '#/components/schemas/post'
 patch:
 description: 'Update post'
 requestBody:
 required: true
 content:
 application/json:
 schema:
 $ref: '#/components/schemas/post'
 parameters:
 - $ref: '#/components/parameters/post-id'
 responses:
 '200':
 description: OK
 content:
 application/json:
 schema:
 $ref: '#/components/schemas/post'
 delete:
 description: 'Delete post'
 parameters:
 - $ref: '#/components/parameters/post-id'
 responses:
 '200':
 description: OK

This file is a minimal OpenAPI description that describes how to call the /posts endpoint in the JSONPlaceholder REST API.

You can then use the Kiota command line tool to generate the API client classes.

kiota generate -l dart -d posts-api.yml -c PostsClient -o ./client

Create the client application

Create a file in the root of the project named cli.dart and add the following code.

import '../client/posts_client.dart';
import '../client/models/post.dart';
import 'package:microsoft_kiota_bundle/microsoft_kiota_bundle.dart';

void main(List<String> arguments) async {
 var authenticationProvider = AnonymousAuthenticationProvider();
 var requestAdapter =
 DefaultRequestAdapter(authProvider: authenticationProvider);
 var client = PostsClient(requestAdapter);

 // GET /posts
 var posts = await client.posts.getAsync();
 print('Posts: ${posts?.length ?? 0}');

 // GET /posts/{id}
 var specificPostId = 5;
 var specificPost = await client.posts.byPostId(specificPostId).getAsync();
 print(
 'Retrieved post - ID: ${specificPost?.id}, Title: ${specificPost?.title}, Body: ${specificPost?.body}');

 // POST /posts
 var newPost = Post();
 newPost.body = 'Hello world';
 newPost.title = 'Testing Kiota-generated API client';
 newPost.userId = 42;
 var createdPost = await client.posts.postAsync(newPost);
 print('Created new post with ID: ${createdPost?.id}');

 // PATCH /posts/{id}
 var updatePost = Post();
 updatePost.title = 'Updated title';
 var updatedPost =
 await client.posts.byPostId(specificPostId).patchAsync(updatePost);
 print(
 'Updated post - ID: ${updatedPost?.id}, Title: ${updatedPost?.title}, Body: ${updatedPost?.body}');

 // DELETE /posts/{id}
 await client.posts.byPostId(specificPostId).deleteAsync();
}

Run the application

To start the application, run the following command in your project directory.

dart run

See also

• kiota-samples repository contains the code from this guide.
• ToDoItem Sample API implements a sample OpenAPI in ASP.NET Core and sample clients in multiple languages.