sourceafIoc::Inject.fan

// Facet Inheritance not applicable with fields - see http://fantom.org/sidewalk/topic/2186
// see TestInjectFacetInheritance
// @FacetMeta { inherited = true } 

** Use in services to inject dependencies and services.
**  - Place on a field to mark it for field injection
**  - Place on a ctor to mark it for use by autobuilding / service creation
facet class Inject { 
    
    ** If 'true' then a *new* instance of the dependency / service is created via 'Registry.autobuild()'.
    ** 
    ** Can be used to *new up* classes that have not been defined as a service.
    ** 
    ** Defaults to 'false'. 
    const Bool autobuild    := false
    
    ** Specifies the (qualified) id of the service to inject. 
    **  
    ** Use when a service mixin has multiple implementations.
    const Str? serviceId
    
    ** If 'true' and the dependency / service does not exist then injection fails silently without causing an Err.
    ** 
    ** Useful when injecting services from (optional) 3rd party libraries. 
    ** 
    ** Defaults to 'false'.
    const Bool optional     := false
}