C++: GetRandomReachablePointInRadius

Hi, I’m really confused with navigation systems. I copied the code from this site: [link text][1]. This is my code:

#include "BaseAiController.h"
#include "Runtime/Engine/Classes/AI/NavigationSystemBase.h"
#include "Runtime/NavigationSystem/Public/NavigationSystem.h"
#include "Runtime/NavigationSystem/Public/AbstractNavData.h"

bool ABaseAiController::GetRandomPointInRadius(const FVector& Origin, float Radius, FVector& OutResult)
	UNavigationSystem* NavSys = UNavigationSystem::GetCurrent(GetWorld());
	if (!NavSys)
		return false;

	FNavLocation Result;
	//This is a wrapper for UE4 version
	bool bSuccess = NavSys->GetRandomPointInRadius(Origin, Radius, Result);

	OutResult = Result.Location;
	return bSuccess;

The error is this: "GetRandomReachablePointInRadius": is no element of "UNavigationSystem". Now if I access NavigationSystem.h, I find this code:

. The strange thing is, the program doesn’t find any functions of the upper box, but “ProjectPointToNavigation” it can find. I tried to get information from the unreal engine wiki, but sadly every time I try to get to this site: https://api.unrealengine.com/INT/API/Runtime/Engine/AI/Navigation/UNavigationSystem/index.html, there is an error :“404 page not found”. What can I do?