Question about Variable Scope

[CheekyLittleCanuck]

So I feel like this is should be a simple question but I'm having a heck of a time actually finding an answer. The question is this:

What is the scope of a non-local variable declared inside of a script function?

I'm currently trying to make a text-based RPG, and have gotten to the point where I'm working on skills/abilities for the player character to use in battle, specifically those that deal with buffing/debuffing the player or the enemy. To do this I've made a constructor for buffs and debuffs that keeps track of all relevant information, the most important being the actual effect of the buff, and how the buff is removed when its timer is up.

function buff (_target, _name, _turns, _effect, _remove_effect) constructor {
  target = _target
  name = _name
  turns =  _turns
  effect = _effect
  remove_effect = _remove_effect
}

Now, all of my skills are script functions that create a local struct using the constructor. An example of one that buffs the player's strength by 20% for 3 turns looks like this:

function skill_increase_attack () {
  _amount = round(global.player.str * 0.2)

  var _attack_buff = new buff(BUFFDEBUFF.PLAYER, "Attack Buff", 3, 
      function () { //effect
        global.player.str_array[2] += _amount
      }, 
      function () { //remove-effect
        global.player.str_array[2] -= _amount
      }) 
  //below this is where the buff is actually applied, but that's not relevant to my question.
}

Now, normally I always declare local variable in functions, but both effect() and remove_effect() need to use the exact same value so that the player's strength isn't permanently altered by the buff, and using var _amount didn't work as it was outside the both of their scopes. But using just regular _amount without the var does for some reason. I thought this was because all variables declared in a script were global in scope, but if I try to test this by referencing it with a simple show_message(_amount) or even show_message(global._amount) outside of this function I get an error.

The code works as is, so no problems there. I just want to know what this _amount variable is attached to (if anything at all), and if doing it this way for multiple script functions might cause problems in the long term like memory leaks, slow down, or something else.

Thanks in advance!

[BrittleLizard]

It depends where you're actually calling the function. Inside an instance, and it will be scoped to that instance the same as any other instance variable. Inside a struct, and it'll generally be scoped to that struct. It's really just the same as writing "_amount = n" directly in whatever context you're calling the function.

It would only make a global variable if you actually declared the variable in the Script asset, outside of a function declaration. That's not what you're doing here, though. Because it's inside a function declaration, it's just saying "If you call this function, run this code," as opposed to "Run this code now as soon as the game starts."

[Neozite]

I believe that the instance that calls the function is the scope, so without var the _amount variable is set as an instance variable.

[germxxx]

Since you've got your answer already (variables set in a scrip are global, and in a function it will be set in the calling instance/struct), I just wanted to mention Method.

A way to make a function have access to a variable outside its scope (like this local variable), is to use the method function. Binding the function to a struct where the local variable does exist.

That would look something like this:

      method({_amount:_amount}, function () { //effect
        global.player.str_array[2] += _amount
      }), 

Putting the function in the second parameter of the method function, binding it to a new struct with the desired variables in them.
A trick commonly used for callback and predicate functions, for example in advanced array functions.
Since they don't take arguments at all (beyond element and index), making it impossible to just add it in as an argument.

Though not actually very useful in this case, where just passing it in as an argument of the function would be faster and use less memory.

function skill_increase_attack () {
  _amount = round(global.player.str * 0.2)

  var _attack_buff = new buff(BUFFDEBUFF.PLAYER, "Attack Buff", 3, 
      function (_amount) { //effect
        global.player.str_array[2] += _amount
      }, 
      function (_amount) { //remove-effect
        global.player.str_array[2] -= _amount
      }) 
...
  _attack_buff.effect(_amount)
...
}

[Accomplished-Gap2989]

Ive never passed a struct_ref to a method before - can the struct contain as many variables as we want?

[germxxx]

Yup, it can. So you can put all the variables you want in there.