How to stop an object from moving past a point - lua

Question

I was wondering if there was a way to stop an object from moving off the screen. In my code, I have a controllable character (player) and I want to prevent it from moving to the left when it's x coordinate is < 1
I have tried to do this in the code below, however, the player will not be stopped if you hold down the left arrow key.
Is there a way to fix this? If I had a guess, I would somehow need my program to continuously check for the case where player.x < 1
motionx = 0; -- Variable used to move character along x axis
speed = 10; -- Set Walking Speed
local function moveplayer (event)
player.x = player.x + motionx;
end
Runtime:addEventListener("enterFrame", moveplayer)
local function onKeyEvent( event )
if ( event.phase == "down" ) then
if ( event.keyName == "left" ) and player.x > 1 then
motionx = -speed
return true
elseif ( event.keyName == "right" ) then
motionx = speed
return true
end
end
end
Runtime:addEventListener( "key", onKeyEvent )

Answer 1

You need to check the boundaries and set the motionx to zero:
local player = display.newCircle(display.contentCenterX, display.contentCenterY, 10)
local motionx = 0; -- Variable used to move character along x axis
local speed = 10; -- Set Walking Speed
local function moveplayer( event )
player.x = player.x + motionx;
if player.x < 0 then
player.x = 0
motionx = 0
elseif player.x > display.contentWidth then
player.x = display.contentWidth
motionx = 0
end
end
Runtime:addEventListener( "enterFrame", moveplayer )
local function onKeyEvent( event )
if event.phase == "down" then
if event.keyName == "left" then
motionx = -speed
return true
elseif event.keyName == "right" then
motionx = speed
return true
end
end
end
Runtime:addEventListener( "key", onKeyEvent )

Answer 2

Simply implement a function that checks your objects position vs your screen boundaries. Whenever it reaches the border of your screen you stop it.
To check your objects position for every frame add your function as an event listener for the event "enterFrame".
Read this for details:
https://docs.coronalabs.com/guide/events/detectEvents/index.html
Of course you can also use the collision engine by placing invisible walls around your screen so your object will bounce back whenever it hits the border.

Answer 3

You were fairly close but may need your whole code to test it. I only changed this player.x < 1 and moved )
motionx = 0; -- Variable used to move character along x axis
speed = 10; -- Set Walking Speed
local function moveplayer (event)
player.x = player.x + motionx;
end
Runtime:addEventListener("enterFrame", moveplayer)
local function onKeyEvent( event )
if ( event.phase == "down" ) then
if ( event.keyName == "left" and player.x < 1) then
motionx = -speed
return true
elseif ( event.keyName == "right" ) then
motionx = speed
return true
end
end
end
Runtime:addEventListener( "key", onKeyEvent )