IoC EnvUser Guide


IoC Env is a library for determining the application environment, be it development, test or production.

It sniffs environment variables and program arguments, and offers a manual override option - useful for testing.

Quick Start

  1. Create a text file called
    using afIoc
    using afIocConfig
    using afIocEnv
    const class Example {
        @Inject                           // --> Inject IocEnv service
        const IocEnv iocEnv
        @Config { id="afIocEnv.isProd" }  // --> Inject Config values
        const Bool isProd
        new make(|This| in) { in(this) }
        Void print() {
            echo("The environment is '${iocEnv.env}'")
            if (isProd) {
                echo("I'm in Production!")
            } else {
                echo("I'm in Development!!")
    // ---- Standard IoC Support Classes ----
    class Main {
        Void main() {
            registry := RegistryBuilder() {
            example  := (Example) registry.dependencyByType(Example#)
  2. Run as a Fantom script from the command line:
    C:\> fan -env PRODUCTION
    [info] [afIocEnv] Setting from environment variable 'env' : development
    [info] [afIocEnv] Overriding from cmd line argument '-env' : PRODUCTION
    The environment is 'PRODUCTION'
    I'm in Production!


IocEnv Injection

The IocEnv class is the main IoC service with handy utility methods. Inject it as usual:

using afIoc::Inject
using afIocEnv::IocEnv

@Inject IocEnv iocEnv


Void wotever() {
   if (iocEnv.isDev) {
      ... // dev only stuff

Config Injection

You can also inject IoC Config values. See IocEnvConfigIds for a complete list of injectable values:

using afIoc::Inject
using afIocConfig::Config

@Config { id="afIocEnv.isDev" }
Bool isDev


Void wotever() {
   if (isDev) {
      ... // dev only stuff

Setting the Environment

To determine your environment, IoC Env checks the following:

  • Environment Variables - if an environment variable named env or environment if found, it is taken to be your environment.
  • Program Arguments - if an option labelled -env or -environment if found, the environment is taken to be the argument following. Example, -env prod. This convention follows @Opt from util::AbstractMain.
  • Manual Override - the environment may be set / overridden when the IocEnv instance is created.

The ordering of checks mean program arguments override environment variables and a manual override trumps everything.

Note if no environment setting is found, it defaults to Production. This is because it's usually easier to configure dev and test boxes than it is to configure production ones. So it is one less thing to worry about!

ALIEN-AID: Because the environment default is production you need to set the environment on your dev machine. The easiest way to do this is to set a new environment variable called ENV to the value dev.

Overriding the Environment

Should you need to programmatically override the environment, do it by overriding the IocEnv service in your AppModule:

using afIoc
using afIocEnv

const class AppModule {

    Void defineServices(RegistryBuilder defs) {