error C2660: 'InputComponent::update': function does not take 1 arguments

[Matiasmunk]

I'm trying to implement a basic Entity Component System into a game that I'm making, however upon trying to do so I came across this error, which usually I can just add the missing paramater in the function prototype.

My InputComponent.h header file:

#pragma once

#include "Player.h"
#include "Keyboard.h"

class InputComponent
{
public:
	InputComponent();
	~InputComponent();
	
	void update(Player& player);

private:
	static const int WALK_ACCELERATION = 1;
};

Here is relevant code from InputComponent.cpp:

void InputComponent::update(Player& player) {
	switch (Keyboard::ArrowKeyDirection())
	{
	case ALLEGRO_KEY_UP:
		player.velocity -= WALK_ACCELERATION;
		break;

	case ALLEGRO_KEY_DOWN:
		player.velocity += WALK_ACCELERATION;
		break;
	case ALLEGRO_KEY_LEFT:
		player.velocity -= WALK_ACCELERATION;
		break;

	case ALLEGRO_KEY_RIGHT:
		player.velocity += WALK_ACCELERATION;
		break;
	}
}

Finally here is Player.h and relevant code from Player.cpp:

#pragma once

#include "stdafx.h"
#include "InputComponent.h"
#include "PhysicsComponent.h"

class Player
{
public:
	Player();
	~Player();
	
	int x, y;
	int velocity;

	//void update(Map& map, Graphics& graphics);
	void update();

private:
	InputComponent input_;
	PhysicsComponent physics_;

};

void Player::update() {
	input_.update(*this);

	x += velocity;
	//Resolve collision on world
}

[wolle]

In InputComponent.h you do #include "Player.h".

And in Player.h you do #include "InputComponent.h".

That is you are including .h files recursively. This usually means trouble and can cause unexpected spurious error messages.

[Matiasmunk]

In InputComponent.h you do #include "Player.h".

And in Player.h you do #include "InputComponent.h".

That is you are including .h files recursively. This usually means trouble and can cause unexpected spurious error messages.

Well I did try that, just removing #include "player.h" from InputComponent.h, another error came from that

1>------ Build started: Project: Game, Configuration: Debug Win32 ------
1>InputComponent.cpp
1>..\inputcomponent.h(11): error C2061: syntax error: identifier 'Player'
1>..\inputcomponent.cpp(11): error C2065: 'Player': undeclared identifier
1>..\inputcomponent.cpp(11): error C2065: 'player': undeclared identifier
1>..\inputcomponent.cpp(11): error C2761: 'void InputComponent::update(void)': redeclaration of member is not allowed
1>..\inputcomponent.cpp(11): error C2448: 'InputComponent::update': function-style initializer appears to be a function definition
1>PhysicsComponent.cpp
1>..\inputcomponent.h(11): error C2061: syntax error: identifier 'Player'
1>Player.cpp
1>..\inputcomponent.h(11): error C2061: syntax error: identifier 'Player'
1>..\player.cpp(12): error C2660: 'InputComponent::update': function does not take 1 arguments
1>Generating Code...
1>Done building project "Game.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

[2kaud]

What you have is basically this

class InputComponent
{
    void update(Player&);
};

class Player
{
    InputComponent input_;
}

Unfortunately, this is a no-no as you have a circular reference. InputComponent depends upon Player which in turn depends upon InputComponent.

Possibly the easiest way in this case is to have InputComponent update() take a pointer argument rather than a reference. This gives

class Player;

class InputComponent
{
    void update(Player*);
};

class Player
{
    InputComponent input_;
}

with the appropriate changes to the .cpp files.

This works as Player is forward referenced as a class and used as a pointer so the compiler doesn't need to know its size as the size of all pointers are the same for the same 32/64 bit build.

[wolle]

Well I did try that, just removing #include "player.h" from InputComponent.h, another error came from that

A recursive dependency is a sign of a design problem called tight coupling. A common way to loosen it up it is to introduce a new class that breaks the dependency.