Circular Reference issue with Swift Suspenders

[tschneidereit]

(copied from http://github.com/robotlegs/robotlegs-framework/issues/#issue/1)

There is a circular reference bug if you have singletons that inject eachother.

Trivial example (Flex Builder 3 AS3 project) here: http://www.stevensacks.net/xfer/circbug.zip

And the output:

undefined

at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at org.swiftsuspenders::Injector/instantiate()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:134]
at org.swiftsuspenders.injectionresults::InjectSingletonResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectSingletonResult.as:59]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]

[benjamincombes]

Same problem for me :
TypeError: Error #1009: Il est impossible d'accéder à la propriété ou à la méthode d'une référence d'objet nul.
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:111]
at org.swiftsuspenders.injectionresults::InjectValueResult/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionresults/InjectValueResult.as:48]
at org.swiftsuspenders::InjectionConfig/getResponse()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/InjectionConfig.as:58]
at org.swiftsuspenders.injectionpoints::PropertyInjectionPoint/applyInjection()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/injectionpoints/PropertyInjectionPoint.as:47]
at org.swiftsuspenders::Injector/injectInto()[/Users/shaun/Documents/Development/Workspaces/GanymedeFB4/SwiftSuspenders/src/org/swiftsuspenders/Injector.as:120]
at fr.benjamincombes.toolbox.configuration::DefaultToolboxInjectorConfiguration/mapDependencies()[/Users/Ben/Documents/Travail/Projets/Toolbox/Toolbox/src/fr/benjamincombes/toolbox/configuration/DefaultToolboxInjectorConfiguration.as:53]
at fr.benjamincombes.toolbox::Toolbox$/init()[/Users/Ben/Documents/Travail/Projets/Toolbox/Toolbox/src/fr/benjamincombes/toolbox/Toolbox.as:26]
at TestRunningApplication/onCreationComplete()[/Users/Ben/Documents/Travail/Projets/Toolbox/Toolbox/tests/TestRunningApplication.mxml:21]
at TestRunningApplication/___TestRunningApplication_Application1_creationComplete()[/Users/Ben/Documents/Travail/Projets/Toolbox/Toolbox/tests/TestRunningApplication.mxml:7]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.core::UIComponent/set initialized()
at mx.managers::LayoutManager/doPhasedInstantiation()
at mx.managers::LayoutManager/doPhasedInstantiationCallback()
Tell me if you source code may help you !

[tschneidereit]

That's actually a different problem not related to what this ticket is about.

Without having any source code, I can't be sure, but my guess would be that the specific bug you're running into has been fixed in the 1.5b1 release (and maybe even in the 1.0.1 release). Can you add the SWC from the latest zip distribution to your projects and check if the problem is resolved by that?
http://github.com/tschneidereit/SwiftSuspenders/downloads

[katopz]

vote for this bug, any work around for this btw? i'm feeling dead here

[tschneidereit]

Having thought about it for quite some time, I don't think there's any feasible way to fix this.

The thing is that circular dependencies are just inherently broken: Both objects need each other to work in a way that the IoC container can't resolve by itself. In theory, a sub-set of cases could in fact be detected and resolved automatically, but I can't come up with a clean and performant implementation of even those.

A future version of SwiftSuspenders will support two things that should help to resolve this, though: optional and live injections. With optional injections, the injector doesn't throw if it can't fulfill a dependency, while with live injections, it will update the injectee as soon as the mapped value it expects changes. With these in place, I should be able to not only detect but also resolve cases of mutually recursive dependencies.