How virtual methods work as method_implementation()?

Development Programming & Scripting
1

Hello,

I started to learn UE4 this week. By the way I am learning C++ basics at the same time so this question can be related to C++ not UE4.

In tutorial of battery collector, author uses virtual methods in parent class to enable children classes to override it.

So it is like that.

parent.h:

UFUNCTION(BlueprintNativeEvent)
void WasCollected();	
virtual void WasCollected_Implementation();

parent.cpp

//no implementation for WasCollected method.

 void APickup::WasCollected_Implementation()
{
	//Some implementation code
}

child.h

	void WasCollected_Implementation() override;

child.cpp

void ABatteryPickup::WasCollected_Implementation()
{

	Super::WasCollected_Implementation();
	//Some code overriding parent method.
}

In another class whole functionality is made by calling WasCollected method even it is just declared header file of parent.

So how is it works. Is _Implementation special key word or something like that for overriding methods. Because as I am looking this code, it shouldn’t work.

2

I assume it’s somehow related to exposing C++ functions to blueprints via reflection.
check out this link: Introduction to C++ Programming in UE4 | Unreal Engine Documentation

especially, this paragraph:
“This version still generates the thunking method to call into the Blueprint VM. So how do you provide the default implementation? The tools also generate a new function declaration that looks like _Implementation(). You must provide this version of the function or your project will fail to link. Here is the implementation code for the declaration above.”