Destroying structs/interfaces..

09-08-2007, 10:07 AM

Just a quick question..

JASS:

struct StructData
    real r = 0//"NORMAL" value
endstruct

function Func takes nothing returns nothing
local StructData d = StructData.create()
    set d.r = 5
    call SetUnitUserData(GetTriggerUnit(), d.r)
    call StructData.destroy(d)
endfunction

If i used call StructData.destroy(struct) will it reset the struct's data back to "normal"? Will the real r be back to 0?

09-08-2007, 10:14 AM	#2
Alexander244	No, that is done when the struct is created. Edit: There is always the onDestroy method, where you could set r to 0.

09-08-2007, 10:26 AM	#3
Anitarf	Wouldn't the correct syntax for destroying that struct be d.destroy()?

09-08-2007, 10:31 AM

Toink

Quote:

There is always the onDestroy method, where you could set r to 0.

But interfaces can't have that method.. :|

09-08-2007, 10:58 AM	#5
Alexander244	Why do you need them to have it? I don't know much about interfaces, but as I understand them they allow you to have any-struct-type.same-method-name() You can already have any-struct-type.destroy() which will call the onDestroy method for that struct type.

09-08-2007, 01:22 PM

Vexorian

Quote:

Originally Posted by Toink

But interfaces can't have that method.. :|

But interface childs can.

--
The only reason you would have to do this would be that you are actually accessing the struct after you destroy it? That's something I would not really recommend to be ever done.

09-08-2007, 01:35 PM

Toink

Well it can't be that bad..

Oh and another question.. if I set d.r to 5 then destroy the struct. Then create another struct of the same structtype(StructData in this case) will the <NewStruct>.r = 5 ?

JASS:


struct structdata
   real r = 1
endstruct

function func2 takes nothing returns nothing
local structdata d
    call TriggerSleepAction(10.)
    set d = structdata.create() //AFAIK, it just gets a pointer to the parallel array
    call BJDebugMsg(R2S(d.r))
endfunction
    

function func takes nothing returns nothing
local structdata d = structdata.create()
    set d.r = 5
    call ExecuteFunc("func2")
    call structdata.destroy()
endfunction

In other words.. will func2 display '5' ?

09-08-2007, 01:43 PM

Vexorian

Quote:

Oh and another question.. if I set d.r to 5 then destroy the struct. Then create another struct of the same structtype(StructData in this case) will the <NewStruct>.r = 5 ?

No,

because of this:

JASS:

struct structdata
   real r = 1
endstruct

Quote:

Well it can't be that bad..

It is terrible. When you destroy an struct you are saying: "I no longer need that id" and that id is going to be recycled, so if you try to access an already destroyed struct you may be accessing a new struct...

10-01-2007, 09:22 PM	#9
xombie	Speaking of structs, when you destroy a struct (which is an integer), what happens to the actual integer value of the struct.

10-01-2007, 09:29 PM

#10

Vexorian

nothing?

Imagine every struct got an stack and an integer variable N=0

when you want to allocate() we first verify, is the stack empty? If the stack is empty, N is increased and the return for allocate() is N.

If the stack is not empty, then we return the stack's top and also remove the top element from the stack.

And .destroy, simply adds the integer id of the struct to the stack, so allocate() can return it once again.

10-01-2007, 10:07 PM

#11

cohadar

If I might add a bit to this discussion.

Structs are global array indexes.
Struct Id's have values in range from 0..8190 (0 means null for structs)

So basically struct (or struct id to be precise) is a subset of integer.
Integer that contains struct id is called this

You don't have to write this you can simply use a dot syntax.

JASS:

struct StructName
    integer xxx
    timer tictac
endstruct

this.x is the same as .x inside a struct

Now remember I said this is actually a struct id,
and I also said struct id's are indexes in global arrays.

Well that is because vJass actually works like this:

this.xxx = 7 <--> s__StructName_xxx[this] = 7
call DestroyTimer(tictac) <--> call DestroyTimer(s__StructName_tictac[this])

s__StructName_xxx and s__StructName_tictac are simple global arrays:

JASS:

globals
    integer array s__StructName_xxx
    timer array s__StructName_tictac
endglobals

As you can see struct with 2 attributes (xxx and tictac) is actually
2 separate global arrays + this

10-01-2007, 10:12 PM	#12
Here-b-Trollz	I'm pretty sure that 'this' is an argument for any function that uses .stuff. Otherwise, you use a.stuff, where a is an integer which you are defining at the beginning of the function, by saying 'local Struct a'. Each struct knows what it is, because, if you call a method which isn't static, then you have to call it instance.func(), or a.func(). Then, it just passes a through as 'this'.

10-01-2007, 10:19 PM

#13

cohadar

Ah yes I forgot that detail, this:
method add takes real a, real b returns real
is actually:

function add takes integer this, takes real a, real b returns real
So when you call a method of a struct:
call SomeStruct.add(1, 2)
it actually is:
call add(SomeStruct, 1, 2)
Struct variables are nothing but integers in range 0..8190 that
contain the this. and they do all they work by passing this around