handling errors

ricvieira

Hi, I have another noob question, I've been trying to understand how to handle errors in gideros, in java we use try/catch blocks to encapsulate what we want to test and deal with the error, in lua I found the pcall function, but it doesnt seem to work that well

if I do this, the pcall works well

function func(n) return 'N'+n; end   if pcall(func, n) then print("worked") else print("Error") end   --->Error

but when I try to use it with gideros functions it doesnt work:

mychild = Bitmap.new(Texture.new("images/image1.png")) if pcall(self:removeChild(), mychild) then print("worked") else print("Error") end   --->start.lua:88: bad argument #1 to 'removeChild' (Sprite expected, got no value)

or if I do like this:

mychild = Bitmap.new(Texture.new("images/image1.png")) if pcall(self:removeChild(mychild)) then print("worked") else print("Error") end     --->start.lua:88: The supplied Sprite must be a child of the caller.

So is there a way to use some kind of try/catch block in gideros, besides pcall, that I can check if a variable is a child of self, or using another self function? or am I using pcall wrong??

tnx in advance

ar2rsawseen

it seems like incorrect usage, can you try this one:

mychild = Bitmap.new(Texture.new("images/image1.png")) if pcall(self.removeChild, self, mychild) then print("worked") else print("Error") end

vitalitymobile

@ricvieira
If you want to use pcall, change to this

mychild = Bitmap.new(Texture.new("images/image1.png")) if pcall(self.removeChild,self,mychild) then print("worked") else print("Error") end

Or you can use this method

mychild:removeFromParent()

vitalitymobile

@ar2rsawseen super fast , when i google and try the code, you have the answer

ricvieira

tnx ar2rsawseen and vitalitymobile

I had tried with both self and mychild has arguments, but I always tried with the "self:removeChild" and not with just the .

but I now read the difference between the two calls, when I use . Im calling the function and passing self has first parameter.

I know about removeFromParent(), Im using that, this was just trying to understand how to handle run time errors with gideros, it wasnt about the removeChild function itself Im still learning

tnx again, you guys rock

OZApps

@ricvieira,
not jumping into the quick draw contest here, for understanding a few things

1. the difference between : and .

object:func()

==> is the same as

object.func(object)

2. about pcall,
there is a difference between

func

and

func()

where

type(func)

is "function" and

type(func())

is the return type of the function. pcall invokes the function and the parameters, so if you pass it func() then it will not work as you are calling the return value as a function which will not work as it is not a function.

Hope that helps you understand pcall and the difference between . and :

ricvieira

yeah, it helps a lot, tnx OZApps, I know from experience that error handling is a really important part of every project, thats why I wanted to understand it better how to do it here in lua/gideros

tnx again, you guys rock, Im loving gideros, not just for the tech itself, but cause of this awesome community, always willing to help and answering noob questions like mine

OZApps

Hi Ricardo @ricvieira, nice to see that blog post http://wait4ideas.wordpress.com/2013/11/02/handling-run-time-errors-in-gideros/