New: Add interface-filtered object references

Add native hard and soft reference types for scene objects that implement
a scripting interface:

- ScriptingObjectInterfaceReference<T>
- SoftObjectInterfaceReference<T>

Source/Engine/Scripting/SoftObjectInterfaceReference.h

@@ -0,0 +1,258 @@
+// Copyright (c) Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#include "Engine/Scripting/SoftObjectReference.h"
+#include "Engine/Scripting/ScriptingObjectInterfaceReferenceUtils.h"
+
+/// <summary>
+/// The scene object soft interface reference. Objects gets referenced on use (ID reference is resolving it).
+/// </summary>
+/// <typeparam name="T">The type of the scripting interface.</typeparam>
+template<typename T>
+API_CLASS(InBuild) class SoftObjectInterfaceReference : public SoftObjectReferenceBase
+{
+    typedef ScriptingObjectInterfaceReferenceHelper<T> Helper;
+
+public:
+    typedef SoftObjectInterfaceReference<T> Type;
+
+public:
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    SoftObjectInterfaceReference()
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    /// <param name="obj">The object to link.</param>
+    SoftObjectInterfaceReference(SceneObject* obj)
+    {
+        OnSet(Helper::IsValidObject(obj) ? obj : nullptr);
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    /// <param name="interfaceObj">The interface object to link.</param>
+    SoftObjectInterfaceReference(T* interfaceObj)
+    {
+        OnSet(Helper::GetSceneObject(interfaceObj));
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    /// <param name="other">The other property.</param>
+    SoftObjectInterfaceReference(const SoftObjectInterfaceReference& other)
+    {
+        OnSet(other.GetID());
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    /// <param name="other">The other property.</param>
+    SoftObjectInterfaceReference(SoftObjectInterfaceReference&& other)
+    {
+        OnSet(other.GetID());
+        other.OnSet(nullptr);
+    }
+
+    /// <summary>
+    /// Finalizes an instance of the <see cref="SoftObjectInterfaceReference"/> class.
+    /// </summary>
+    ~SoftObjectInterfaceReference()
+    {
+    }
+
+public:
+    FORCE_INLINE bool operator==(SceneObject* other)
+    {
+        return GetObject() == other;
+    }
+
+    FORCE_INLINE bool operator!=(SceneObject* other)
+    {
+        return GetObject() != other;
+    }
+
+    FORCE_INLINE bool operator==(T* other)
+    {
+        return Get() == other;
+    }
+
+    FORCE_INLINE bool operator!=(T* other)
+    {
+        return Get() != other;
+    }
+
+    FORCE_INLINE bool operator==(const SoftObjectInterfaceReference& other)
+    {
+        return GetID() == other.GetID();
+    }
+
+    FORCE_INLINE bool operator!=(const SoftObjectInterfaceReference& other)
+    {
+        return GetID() != other.GetID();
+    }
+
+    SoftObjectInterfaceReference& operator=(const SoftObjectInterfaceReference& other)
+    {
+        if (this != &other)
+            OnSet(other.GetID());
+        return *this;
+    }
+
+    SoftObjectInterfaceReference& operator=(SoftObjectInterfaceReference&& other)
+    {
+        if (this != &other)
+        {
+            OnSet(other.GetID());
+            other.OnSet(nullptr);
+        }
+        return *this;
+    }
+
+    FORCE_INLINE SoftObjectInterfaceReference& operator=(SceneObject* other)
+    {
+        OnSet(Helper::IsValidObject(other) ? other : nullptr);
+        return *this;
+    }
+
+    FORCE_INLINE SoftObjectInterfaceReference& operator=(T* other)
+    {
+        OnSet(Helper::GetSceneObject(other));
+        return *this;
+    }
+
+    FORCE_INLINE SoftObjectInterfaceReference& operator=(const Guid& id)
+    {
+        OnSet(id);
+        return *this;
+    }
+
+    /// <summary>
+    /// Implicit conversion to the interface.
+    /// </summary>
+    FORCE_INLINE operator T*() const
+    {
+        return Get();
+    }
+
+    /// <summary>
+    /// Implicit conversion to boolean value.
+    /// </summary>
+    FORCE_INLINE operator bool() const
+    {
+        return Get() != nullptr;
+    }
+
+    /// <summary>
+    /// Interface accessor.
+    /// </summary>
+    FORCE_INLINE T* operator->() const
+    {
+        return Get();
+    }
+
+    /// <summary>
+    /// Gets the object as a given type (static cast).
+    /// </summary>
+    template<typename U>
+    FORCE_INLINE U* As() const
+    {
+        return static_cast<U*>(GetObject());
+    }
+
+public:
+    /// <summary>
+    /// Gets the interface pointer.
+    /// </summary>
+    FORCE_INLINE T* Get() const
+    {
+        return ScriptingObject::ToInterface<T>(GetObject());
+    }
+
+    /// <summary>
+    /// Gets the referenced object.
+    /// </summary>
+    SceneObject* GetObject() const
+    {
+        if (!_object)
+            const_cast<SoftObjectInterfaceReference*>(this)->OnResolve(SceneObject::GetStaticClass());
+        return Helper::IsValidObject(static_cast<SceneObject*>(_object)) ? static_cast<SceneObject*>(_object) : nullptr;
+    }
+
+    /// <summary>
+    /// Gets managed instance object (or null if no object linked).
+    /// </summary>
+    MObject* GetManagedInstance() const
+    {
+        auto object = GetObject();
+        return object ? object->GetOrCreateManagedInstance() : nullptr;
+    }
+
+    /// <summary>
+    /// Determines whether object is assigned and managed instance of the object is alive.
+    /// </summary>
+    bool HasManagedInstance() const
+    {
+        auto object = GetObject();
+        return object && object->HasManagedInstance();
+    }
+
+    /// <summary>
+    /// Gets the managed instance object or creates it if missing or null if not assigned.
+    /// </summary>
+    MObject* GetOrCreateManagedInstance() const
+    {
+        auto object = GetObject();
+        return object ? object->GetOrCreateManagedInstance() : nullptr;
+    }
+
+    /// <summary>
+    /// Copies the object ID into the raw storage.
+    /// </summary>
+    FORCE_INLINE void CopyID(uint32 id[4]) const
+    {
+        const Guid value = GetID();
+        memcpy(id, &value, sizeof(uint32) * 4);
+    }
+
+    /// <summary>
+    /// Sets the object.
+    /// </summary>
+    /// <param name="id">The object ID. Uses Scripting to find the registered object of the given ID.</param>
+    FORCE_INLINE void Set(const Guid& id)
+    {
+        OnSet(id);
+    }
+
+    /// <summary>
+    /// Sets the object.
+    /// </summary>
+    /// <param name="object">The object.</param>
+    FORCE_INLINE void Set(SceneObject* object)
+    {
+        OnSet(Helper::IsValidObject(object) ? object : nullptr);
+    }
+
+    /// <summary>
+    /// Sets the object.
+    /// </summary>
+    /// <param name="interfaceObj">The interface object.</param>
+    FORCE_INLINE void Set(T* interfaceObj)
+    {
+        OnSet(Helper::GetSceneObject(interfaceObj));
+    }
+};
+
+template<typename T>
+uint32 GetHash(const SoftObjectInterfaceReference<T>& key)
+{
+    return GetHash(key.GetID());
+}