Lua arguments passed to function in table are nil

Question

I'm trying to get a handle on how OOP is done in Lua, and I thought I had a simple way to do it but it isn't working and I'm just not seeing the reason. Here's what I'm trying:

Person = { };
function Person:newPerson(inName)
  print(inName);
  p = { };
  p.myName = inName;
  function p:sayHello()
    print ("Hello, my name is " .. self.myName);
  end
  return p;
end

Frank = Person.newPerson("Frank");
Frank:sayHello();

FYI, I'm working with the Corona SDK, although I am assuming that doesn't make a difference (except that's where print() comes from I believe). In any case, the part that's killing me is that inName is nil as reported by print(inName)... therefore, myName is obviously set to nil so calls to sayHello() fail (although they work fine if I hardcode a value for myName, which leads me to think the basic structure I'm trying is sound, but I've got to be missing something simple). It looks, as far as I can tell, like the value of inName is not being set when newPerson() is called, but I can't for the life of me figure out why; I don't see why it's not just like any other function call.

Any help would be appreciated. Thanks!

Nicol Bolas · Accepted Answer · 2011-12-22 06:23:15Z

11

Remember that this:

function Person:newPerson(inName)

Is equivalent to this:

function Person.newPerson(self, inName)

Therefore, when you do this:

Person.newPerson("Frank");

You are passing one parameter to a function that expects two. You probably don't want newPerson to be created with :.

answered Dec 22, 2011 at 6:23

Nicol Bolas

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Oliver · Accepted Answer · 2011-12-22 06:11:09Z

10

Try

Frank = Person:newPerson("Frank");

answered Dec 22, 2011 at 6:11

Oliver

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2 Comments

Frank W. Zammetti Over a year ago

I wish I could accept both yours and Nicol's answers as correct, you both got it precisely right... I'm giving it to you just because you answered first :) But thank you Nicol for explaining it too... it was, as I expected, something silly that I just flat-out forgot, not even something I didn't know. Thanks again, everything working as it should and how I want now :)

karthik Over a year ago

@ Schollii: Try to explain your answers in stackoverflow forum.

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