A full-stack Dart application using Flutter on the client and shelf on the server. The Flutter app itself is still the counter app, but the actual number is stored on the server and incremented over HTTP using transport data classes understood by both the Flutter client and shelf server.

The goal of this sample is to demonstrate the mechanics of sharing business logic between a Flutter client and a Dart server. The sample also includes a slightly modified Dockerfile which is required to build a Docker image from a Dart app containing nested packages.

The sample's project structure is as follows:

code_sharing/
  # Flutter app
  client/
    lib/
      ...
    pubspec.yaml
    ...
  # Shelf
  server/
    bin/
      server.dart
    pubspec.yaml
    Dockerfile
  # Common business logic
  shared/
    pubspec.yaml
    lib/
      ...

Recreating this introductory project for yourself can be done in several steps.

1. Create a parent directory, likely sharing a name with your project or product, which will contain everything.

2. Within that directory, run flutter create client. You may also name this Flutter project app, mobile, <project-name>-app or anything else that seems appropriate. At this point, your folder structure should look like this:

   my_project/
     client/
       lib/
         main.dart
       pubspec.yaml
       ...
   

3. From the same location where you ran flutter create, run dart create -t server-shelf server. You may also name this Shelf project, backend, api, <project-name>-server, or anything else that seems appropriate. At this point, your folder structure should look like this:

   my_project/
     client/
       lib/
         main.dart
       pubspec.yaml
       ...
     server/
       bin/
         server.dart
       Dockerfile
       pubspec.yaml
       ...
   

4. Enter your server directory (cd server), and run dart create -t package shared. You may also name this package common, domain, <project-name>-shared, or anything else that seems appropriate. At this point, your folder structure should resemble the sample:

   my_project/
     client/
       lib/
         main.dart
       pubspec.yaml
       ...
     server/
       bin/
         server.dart
       shared/
         lib/
           src/
             ...
           shared.dart
         pubspec.yaml
         ...
       Dockerfile
       pubspec.yaml
       ...
   

5. Next, begin granting access to your shared code by making the following edits to your Flutter app's pubspec.yaml file. Open that file (client/pubspec.yaml) and add the following dependency under the dependencies block:

   dependencies:
     # Add these two lines:
     shared:
       path: ../server/shared
   

6. Next, finish granting access to your shared code by making the following edits to your server's pubspec.yaml file. Open that file (server/pubspec.yaml) and add the following dependency under the dependencies block:

   dependencies:
     # Add these two lines:
     shared:
       path: ./shared
   

7. The final step is to adjust your Dockerfile, as it can no longer successfully run dart pub get after only copying over the pubspec.yaml file (that command now requires the entirety of your shared directory to be present.

• Find the line that says COPY pubspec.* ./, and change it to COPY . ..

With that, you're ready to build and run the app.

To run the sample, or an equivalent you've reconstructed yourself, choose a runtime method below based on your needs.

In one terminal window, run the following commands:

cd my_project/server
dart run bin/server.dart

In a separate terminal window, run the following commands:

cd my_project/client
flutter run

Note: If you named your mobile client and backend servers something other than client and server, you will need to substitute in those values above.

To build your server's Docker image, run the following commands in a terminal window:

cd my_project/server
docker build . -t my_project_server

To run that image as a Docker container, run the following commands in a terminal window:

docker run -it my_project_server

If you have docker-compose installed on your machine, you can run the following command to build and launch your server:

cd my_project
docker-compose up -d

And then later stop the server with:

docker-compose stop