IoC ConfigUser Guide

Overview

IoC Config is an IoC library for providing injectable config values.

Config values are essentially constants, but their value may be overridden on registry startup.

This makes them great for use by 3rd party libraries. The libraries can set sensible default values, and applications may then optionally override them.

Quick Start

1. Create a text file called Example.fan

   using afIoc
   using afIocConfig
   
   internal class Example {
       @Config { id="my.config" }
       Str? myConfig
   }
   
   internal class OtherModule {
       @Contribute { serviceType=FactoryDefaults# }
       static Void contributeFactoryDefaults(Configuration config) {
           config["my.config"] = "3rd party libraries set Factory defaults"
       }
   }
   
   internal class AppModule {
       @Contribute { serviceType=ApplicationDefaults# }
       static Void contributeApplicationDefaults(Configuration config) {
           config["my.config"] = "Applications override Factory defaults"
       }
   }
   
   internal class Main {
       Void main() {
           registry := RegistryBuilder().addModules([ConfigModule#, AppModule#, OtherModule#]).build.startup
           example  := (Example) registry.autobuild(Example#)
   
           echo("--> ${example.myConfig}")  // --> Applications override Factory defaults
   
           registry.shutdown()
       }
   }
   

2. Run Example.fan as a Fantom script from the command line:

   C:\> fan Example.fan
   
   [afIoc] Adding module definition for afIocConfig::AppModule
   [afIoc] Adding module definition for afIocConfig::OtherModule
   [afIoc] Adding module definition for afIocConfig::IocConfigModule
      ___    __                 _____        _
     / _ |  / /_____  _____    / ___/__  ___/ /_________  __ __
    / _  | / // / -_|/ _  /===/ __// _ \/ _/ __/ _  / __|/ // /
   /_/ |_|/_//_/\__|/_//_/   /_/   \_,_/__/\__/____/_/   \_, /
                               Alien-Factory IoC v2.0.0 /___/
   
   IoC Registry built in 281ms and started up in 18ms
   
   --> Applications override Factory defaults
   
   [afIoc] IoC shutdown in 17ms
   [afIoc] "Goodbye!" from afIoc!

Usage

Define Config Values

All config values are referenced by a unique config id (a string). This id is used to set a factory default value, application values and to inject the value in to a service.

Start by setting a default value by contributing to the FactoryDefaults service in your AppModule:

@Contribute { serviceType=FactoryDefaults# }
static Void contributeFactoryDefaults(Configuration config) {
    config["configId"] = "666"
}

Config's may take any value as long as it is immutable (think const class).

Anyone may then easily override your value by contributing to the ApplicationDefaults service:

@Contribute { serviceType=ApplicationDefaults# }
static Void contributeApplicationDefaults(Configuration config) {
    config["configId"] = "69"
}

Inject Config Values

Use the @Config facet to inject config values into your service.

class MyService {
    @Config { id="configId" }
    File configValue

    ...
 }

Note that when config values are injected, they are Type coerced to the field type. That means you can contribute Str or Uri values and inject them as a File.

If @Config does not supply an id then it is determined from the field name, class name and pod name. For example, if Type MyService was in a pod called acme and looked like:

class MyService {
    @Config
    File configValue

    ...
 }

Then the following IDs would be looked up (in order):

<field>                --> configValue
<pod>.<field>          --> acme.configValue
<pod>.<class>.<field>  --> acme.MyService.configValue
<class>.<field>        --> MyService.configValue

(Note that config IDs are case insensitive.)

If the config value is still not found then, as a last resort, the field name is checked against the config IDs after they have been stripped of any non-alphaNum characters. That means you can inject config values with IDs similar to afIocEnv.isDev with:

@Config Bool afIocEnvIsDev