Fix an issue with singleton's getting GC'd

classes.nimble

@@ -1,5 +1,5 @@
 # Package
-version       = "0.3.16"
+version       = "0.3.17"
 author        = "jjv360"
 description   = "Adds class support to Nim."
 license       = "MIT"

src/classes/plugin_singleton.nim

@@ -17,21 +17,36 @@ proc injectSharedAccessor(classDef : ClassDescription) =
         return
 
     # Create a function called shared() which returns a single instance of this class
+    var sharedInstanceVarName = ident("__sharedInstance_" & $classDef.name)
     var methodDef = Method()
     let className = classDef.name
     methodDef.definition = quote do: 
         method shared*() : `className`
     methodDef.body = quote do: 
-        var singletonInstance {.global.} : `className` = nil
-        if singletonInstance == nil: singletonInstance = `className`.init()
-        return singletonInstance
+        if `sharedInstanceVarName` == nil: `sharedInstanceVarName` = `className`.init()
+        return `sharedInstanceVarName`
     methodDef.isStatic = true
     classDef.methods.definitions.add(methodDef)
 
+## Inject the shared variable into the class body
+proc injectSharedVar(classDef : ClassDescription) =
+
+    # Stop if not a singleton
+    if classDef.macroName != "singleton":
+        return
+
+    # Add the code before the method bodies
+    var sharedInstanceVarName = ident("__sharedInstance_" & $classDef.name)
+    var className = classDef.name
+    classDef.outputForwardDeclarations.add(quote do:
+        var `sharedInstanceVarName` : `className` = nil
+    )
+
 
 ## Register the plugin at compile-time
 static:
     classCompilerPlugins.add(proc(stage : ClassCompilerStage, classDef : ClassDescription) =
         if stage == ClassCompilerGatherDefinitions: injectSharedAccessor(classDef)
+        if stage == ClassCompilerGenerateCode: injectSharedVar(classDef)
     )
 

test.nim

@@ -657,6 +657,17 @@ singleton Singleton2 of Singleton1:
 
     method myFunc(): int = 6
 
+## Ensure only one class is created
+var singletonCounter = 0
+singleton SingleTest:
+    method init() = singletonCounter += 1
+    method deinit() = singletonCounter -= 1
+    method test() = discard
+SingleTest.shared.test()
+SingleTest.shared.test()
+assert(SingleTest.shared == SingleTest.shared, "Only one instance of a singleton should exist.")
+assert(singletonCounter == 1, "Singleton constructor should only run once")
+
 test "Subclassing"
 assert(Singleton2.shared.v1 == 3)
 assert(Singleton2.shared.v2 == 4)