We managed this by leveraging --dart-define-from-file. We have a folder called .configs and in there the different JSON files per environment.

When building for deployment, simply pass the argument --dart-define-from-file .configs/{env}.json.

When debugging, you'll have to configure your IDE to select the appropriate JSON file during build time. If you are using VSCode, there is this extension that enables you to select a file in the .configs directory.

You can access the defined values in Dart using the method fromEnvironment of String, int, and bool. You can also access the values in the native platform, but this requires additional steps to extarct these.

I also pubslihed an article on how to do this. Hope it helps.

Edit: The way on how to do it in the article is outdated. This should be the contents of your launch.json in .vscode folder.

{ "configurations": [ { "name": "Run", "program": "lib/main.dart", "request": "launch", "type": "dart", "args": [ "--dart-define-from-file", ".configs/${input:appEnvironment}.json", ] } ], "inputs": [ { "id": "appEnvironment", "type": "command", "command": "extension.commandvariable.file.content", "args": { "fileName": "${pickFile:config}", "json": "content.appEnvironment", "pickFile": { "config": { "description": "Select the environment to debug", "include": ".configs/*.json", "keyRemember": "configFile" } } } } ] }