Javascript proxy object
UObjects are living in UnrealEngine and being reflected into JavaScript as proxy objects. Every instance you access in JavaScript is a proxy object which holds a reference to a underlying UObject. But even proxy object is capable of having extra data because it is a form of JavaScript object.
let obj = new USomeUnrealObject()
obj.NotDeclaredWithinEngine = { x:1, y:2 }
let parent = new USomeParentUnrealObject()
parent.ObjectPropertyVar = obj
// This works!
console.log(parent.ObjectProperty.NotDeclaredWithinEngine) Proxy objects are mortal by design(to save memory footprint), so it can be GC'ed at any time. This may introduce some chaos.
let parent = null
(function() {
let obj = new USomeUnrealObject()
obj.NotDeclaredWithinEngine = { x:1, y:2 }
parent = new USomeParentUnrealObject()
parent.ObjectPropertyVar = obj
})()
// Hey V8, please gc!
gc()
// This doesn't work!
console.log(parent.ObjectProperty.NotDeclaredWithinEngine) To avoid this inconsistency, proxy objects should be kept in somewhere to tell V8 that these objects cannot be GC'ed.
let parent = null
let precious = []
(function() {
let obj = new USomeUnrealObject()
obj.NotDeclaredWithinEngine = { x:1, y:2 }
precious.push(obj)
parent = new USomeParentUnrealObject()
parent.ObjectPropertyVar = obj
})()
// Hey V8, please gc!
gc()
// This works again!
console.log(parent.ObjectProperty.NotDeclaredWithinEngine)