Game cannot process expression "this"

I am trying to get monsters, Pokemon, to spawn in my game. I keep getting errors.

Error running script: Error compiling expression 'this': Unknown object or variable 'this'

This is my code.

https://i.imgur.com/hUSbgRP.png
https://i.imgur.com/GWOSWcH.png

Game link.
http://textadventures.co.uk/games/view/5jllte-m4e2e2whw4gf5jq/pokemon-type-harley-johto-and-sinnoh


Could you click on the code view button, and copy-and-paste that? Even if it means nothing to you, it is easier for us (well me) to see what is going on.


Okay.

roll = GetRandomInt(1,100)
firsttime {
  if (roll > 0 and roll < 26) {
    SpawnSentret (this)
  }
  else if (roll > 25 and roll < 51) {
    SpawnHoothoot (this)
  }
  else if (roll > 50 and roll < 76) {
    SpawnSpinarak (this)
  }
}
otherwise {
  if (roll > 0 and roll < 21) {
    SpawnSentret (this)
  }
  else if (roll > 20 and roll < 41) {
    SpawnHoothoot (this)
  }
  else if (roll > 40 and roll < 61) {
    SpawnSpinarak (this)
  }
}

That looks fine. Could it be in one of the three functions SpawnSentret, etc.?


In the code shown in your first two screenshots, and in the downloaded game, you use the variable object without defining it.

In the code in your second post, you change object to this, which should work fine.

Can you confirm which one you're testing on?


Can you confirm which one you're testing on?

Both.


Can I use something other than "this"?


So, if you use the variable name this in the code, you get an error that Quest doesn't know what you mean by this.

If you use the variable name object in the code, you get an error that Quest doesn't know what you mean by this.

That tells you right away that you're looking in the wrong place for the error. If it says it doesn't know what this is, then the error must be somewhere you're using this.

Let's look at your spawn functions.

    obj.hitpoints = 20
    obj.max = 20
    obj.damage = 2
    obj.maxdamage = 2

yep, that all looks fine. You've got a variable named obj which contains the new Pokemon you're creating, and you're setting its attributes.

And then after a few lines more of that:

    this.firearmdamage = 4
    this.firearmattack = 2

There is no variable this inside that function. That's your error; it should be obj like all the lines above it.


"this" doesn't work in my other functions either.

I have a function called "instantkill." It looks like this:

this.dead = true
msg ("The Pokemon whited out!")
AddToInventory (this)

mrangel's code doesn't work either. I don't know what's wrong.

I think my game is just broken somehow.


'this' is a built-in Object Reference/Pointer Variable VARIABLE to the parent Object of the scripting that you use 'this' within

<object name="orc">

  <attr name="attack" type="script">
    // this = orc
    this.life = this.life - player.damage
  </attr>

</object>

<object name="ogre">

  <attr name="attack" type="script">
    // this = ogre
    this.life = this.life - player.damage
  </attr>

</object>

you can also set 'this' to whatever you want manually as well:

<object name="orc">

  <attr name="attack" type="script">
    this = ogre
    this.life = this.life - player.damage
  </attr>

</object>

<object name="ogre">

  <attr name="attack" type="script">
    this = orc
    this.life = this.life - player.damage
  </attr>

</object>

'this' is a Variable VARIABLE, meaning it's a local Variable, so it has a limited and confusing scope

http://docs.textadventures.co.uk/quest/blocks_and_scripts.html (this might have some relevance on helping understanding its scope)

hopefully, others can explain where/when/what it works vs doesn't work, as I have trouble myself with understanding scope still


"this" doesn't work in my other functions either.

In a verb this means the object the verb is being used on.

In a command this means the command

In an room's enter/exit script this means the room

In a function this is meaningless. You need to specify which object you want to use.


I'm just going to try the room and see what happens.


mrangel's code doesn't work either. I don't know what's wrong.

image

It looks like you're calling SpawnSentret with an undefined (or non-existent) variable/parameter (object).

Like mrangel says: In [a] room's enter/exit script this means the room.

There is no object variable in that script, so the function you call throws an error due to a lack of parameter.

So, first off, change every instance of object back to this in your "After entering" script.

Then, well, I don't know how the function you are calling (SpawnSentret) works, but I assume its parameter needs to be a room.

So, like . . .

Time out.


1 minute later:

I just downloaded your game, unzipped it, and opened the aslx file in a text editor.

Here is the SpawnSentret function:

  <function name="SpawnSentret" parameters="room"><![CDATA[
    if (HasInt(game, "crittercount")) {
      game.crittercount = game.crittercount + 1
    }
    else {
      game.crittercount = 1
    }
    create ("crittercount" + game.crittercount)
    obj = GetObject("crittercount" + game.crittercount)
    obj.parent = room
    obj.displayverbs = Split("Look at;Attack;Direct Hit;Stat;Status", ";")
    obj.dead = false
    obj.hero = false
    obj.changedhitpoints => {
      if (this.hitpoints < 1) {
        this.dead = true
        msg ("It whited out!")
        player.exp = player.exp + 20
        player.pokedollar = player.pokedollar + 5
        roll2 = GetRandomInt(1,20)
        pokeroll = player.catchrate + roll2
        if (pokeroll > 16) {
          if (player.team > 7) {
            MoveObject (this, PC)
            this.displayverbs = Split("Look at;Equip;Reload", ";")
            msg ("object.alias was moved to the PC.")
          }
          else {
            this.displayverbs = Split("Look at;Equip;Reload", ";")
            AddToInventory (this)
          }
        }
        else {
          RemoveObject (this)
        }
      }
    }
    obj.element = "Normal"
    obj.alias = "Sentret"
    obj.listalias = CapFirst(obj.alias)
    obj.look = ProcessText("A " + obj.alias + ". A normal type. A very cautious Pokémon, it raises itself up using its tail to get a better view of its surroundings.")
    obj.critdesc = "A well-placed blow by #attacker# sends you reeling (#hits# hits)."
    obj.attackdesc = "#Attacker# hits you (#hits# hits)."
    obj.missdesc = "#Attacker# misses you."
    obj.hitpoints = 20
    obj.max = 20
    obj.damage = 3
    obj.maxdamage = 3
    obj.attack = 1
    obj.maxattack = 1
    obj.defence = 0
    obj.maxdefence = 0
    obj.armour = 0
    obj.maxarmour = 0
    obj.speed = 10
    obj.maxspeed = 10
    obj.contestpoints = 100
    obj.maxcontestpoints = 100
    obj.tough = 5
    obj.maxtough = 5
    obj.beauty = 6
    obj.maxbeauty = 6
    obj.cool = 4
    obj.cool = 4
    obj.smart = 2
    obj.smart = 2
    obj.cute = 4
    obj.cute = 4
    obj.trainerpoke = false
    obj.faint = false
    obj.element1 = "normal"
    obj.selectweapon => {
      this.weapon = GetObject(PickOneString("Struggle;Quick Attack;Scratch"))
    }
    obj.selectattack => {
      this.weapon = GetObject(PickOneString("Struggle;Quick Attack;Scratch"))
    }
    this.firearmdamage = 4
    this.firearmattack = 2
    this.ammo = 20
    this.ammomax = 20
    // ProcessText("A " + obj.alias + ",t}.")
  ]]></function>



I see the same thing mrangel and HK and Pixie see. These are your last 12 lines of code in that function:

    obj.element1 = "normal"
    obj.selectweapon => {
      this.weapon = GetObject(PickOneString("Struggle;Quick Attack;Scratch"))
    }
    obj.selectattack => {
      this.weapon = GetObject(PickOneString("Struggle;Quick Attack;Scratch"))
    }
    this.firearmdamage = 4
    this.firearmattack = 2
    this.ammo = 20
    this.ammomax = 20
    // ProcessText("A " + obj.alias + ",t}.")

As others have pointed out, you define the variable obj early in the code, but the variable this does not exist in this script.

I see how someone could easily get confused, though (because it seems like this exists in the "After entering" script):

    obj.selectattack => {
      this.weapon = GetObject(PickOneString("Struggle;Quick Attack;Scratch"))
    }

That bit of code is actually creating a selectattack script for whatever obj points to. In that selectattack script, this will work because that script is an attribute on an object. As others have said, when a script is an attribute on an object (like a verb script), this will point to the object to which the script attribute belongs.

But this is not defined in your "After entering room" script. So, like others said, those last 4 lines of code (not counting the last line -- which is commented out) should use the obj variable (which you definitely do define in this script), like this:

    obj.firearmdamage = 4
    obj.firearmattack = 2
    obj.ammo = 20
    obj.ammomax = 20
    // ProcessText("A " + obj.alias + ",t}.")

I think my game is just broken somehow.

Well...

If you weren't playing Solitaire and watching two YouTube videos while you were editing the game, it would probably work better! (Just kidding!!!)


I just set it to "Route 24", the room name, and it worked.

Thank you all.


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