Moving common functions to external module...

Solar2D Lua Language
1

I have a few often used functions I want to get out of my code. One example is a Back button I end up with on many of my scenes. 

I am already following this tutorial for my variables : http://coronalabs.com/blog/2013/05/28/tutorial-goodbye-globals/

and I understand that I can actually store functions there as well. Ref : https://coronalabs.com/blog/2011/09/05/a-better-approach-to-external-modules/

So with that, I moved the following code snippet into my globals holding lua file. It now looks like the following : 

--my global variables space local widget = require( "widget" ) local M = {} local createBackBtn = function(left, top) local backBtn = widget.newButton{ id = "back", left = left, top = top, defaultFile = "images/outline/previous.png", overFile = "images/solid/previous.png", width = 12, height = 20, onRelease = goBack } return backBtn end -- assign a reference to the above local function M.createBackBtn = createBackBtn return M

Now in each screen that requires a back button I simply put the following line and get my back button : 

backBtn = myGlobals.createBackBtn(leftPos, topPos)

This works great and the button is created as expected. My only problem is the function that the button is supposed to call in the onRelease event. I have a function that I always call goBack which gets called by the button. Since the goBack function differs from scene to scene I can’t move it to my external module. So my backBtn’s onRelease event needs to call a function that lives in the scope that called it in the first place.

The button created through the external function above can’t see the goBack function in the calling code. I tried to use the parent. construct but could not get it to work. I would love to get some lua help on this one. 

Thank you very much. 

2

Ok. Solved the problem. The trick is to put the call back function in as a parameter. Sorry for the trouble.

3

Ok. Solved the problem. The trick is to put the call back function in as a parameter. Sorry for the trouble.

4

Good!

I have the same problem. Please could you explain in detail how you solved it. Maybe attaching a bit of code used? 

Thank you,

Regards

-jospic

5

To be honest, I wouldn’t hold functions in globals unless I had a really good reason. It’s generally much better to put them in their own files, and then include them and shortcut them into globals.

-- globals.lua local backButton = require("ui.backbutton") local globals = {} globals.var1 = "happy" -- etc globals.makeBackButton = backButton.make return globals

And jospic, I think what he solved was by doing this:

local makeBackButton(x, y, callback) local backBtn = widget.newButton{ id = "back", left = left, top = top, defaultFile = "images/outline/previous.png", overFile = "images/solid/previous.png", width = 12, height = 20, onRelease = callback, } return backBtn end

That way, you can attach an onRelease function from wherever you are in the code.

6

Good!

I have the same problem. Please could you explain in detail how you solved it. Maybe attaching a bit of code used? 

Thank you,

Regards

-jospic

7

To be honest, I wouldn’t hold functions in globals unless I had a really good reason. It’s generally much better to put them in their own files, and then include them and shortcut them into globals.

-- globals.lua local backButton = require("ui.backbutton") local globals = {} globals.var1 = "happy" -- etc globals.makeBackButton = backButton.make return globals

And jospic, I think what he solved was by doing this:

local makeBackButton(x, y, callback) local backBtn = widget.newButton{ id = "back", left = left, top = top, defaultFile = "images/outline/previous.png", overFile = "images/solid/previous.png", width = 12, height = 20, onRelease = callback, } return backBtn end

That way, you can attach an onRelease function from wherever you are in the code.