View source for 2D Space Shooter Part 4: Player

__TOC__
It is time to make our ship controllable. Since only the player's ship will be controllable, let's make a subclass of our generic Ship to handle that. We will call it 'PlayerShip'.

Go ahead and create a new file named 'player.lua'. This new file will depend on the Ship class, so right click on the file name in gideros studio and access 'Code dependencies'. From there tell Gideros that player.lua will depend on ships.lua.

== Player control ==
The code if this file is rather simple: we register mouse events and react upon them:
<syntaxhighlight lang="lua">
PlayerShip=Core.class(Ship)

function PlayerShip:init()
	self:addEventListener(Event.MOUSE_DOWN,self.onMouseDown,self)
	self:addEventListener(Event.MOUSE_UP,self.onMouseUp,self)
	self:addEventListener(Event.MOUSE_MOVE,self.onMouseMove,self)
	self:addEventListener(Event.MOUSE_HOVER,self.onMouseMove,self)
end

function PlayerShip:destroy()
	self:removeEventListener(Event.MOUSE_DOWN,self.onMouseDown,self)
	self:removeEventListener(Event.MOUSE_UP,self.onMouseUp,self)
	self:removeEventListener(Event.MOUSE_MOVE,self.onMouseMove,self)
	self:removeEventListener(Event.MOUSE_HOVER,self.onMouseMove,self)
	-- Call the inherited destructor
	Ship.destroy(self)
end

function PlayerShip:onMouseDown(event)
	-- Start firing
	self.fire=true
end

function PlayerShip:onMouseUp(event)
	-- Stop firing
	self.fire=false
end

function PlayerShip:onMouseMove(event)
	-- Clamp the position to something in the screen
	local x=(event.x<>(SCR_LEFT+64))><(SCR_RIGHT-64)
	local y=(event.y<>(SCR_TOP+64))><(SCR_BOTTOM-64)
	self:setPosition(x,y)
end
</syntaxhighlight>

Notice how we explicitly call the Ship.destroy() function from our subclass. Also note another use of the <> et >< Gideros operators when clamping the player ship position on screen.

== Using our controllable ship ==
This is were OOP power shines. The only thing you need to do to make the ship you added to main.lua controllable is just to instanciate a PlayerShip instead of a generic Ship. In main.lua, change:
<syntaxhighlight lang="lua">
	local player=Ship.new()
</syntaxhighlight>

into:
<syntaxhighlight lang="lua">
	local player=PlayerShip.new()
</syntaxhighlight>

and you are done!

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'''Prev.: [[2D_Space_Shooter_Part_3:_Ships]]'''</br>
'''Next: [[2D Space Shooter Part 5: Firing]]'''

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