Inheritance in JASS

[Ayanami]

Wanted to know how Inheritance exactly works in JASS. Let's say you have struct Parent and struct Child, I understand that the Child inherits instance members and methods only, right?

I'm confused about the constructor part. If you call [ljass]local Child c = Child.create()[/ljass], this calls Parent's [ljass].create[/ljass] method? Would that mean the variable c holds Parent's instance or Child's instance? I would like to know how exactly the constructor works for a Child & Parent.

Another question:

struct Parent
endstruct

struct Child extends Parent
endstruct

function Test takes nothing returns nothing
    local Parent p = Child.create() // legal?
endfunction

If the above is legal, let's say I have a new scenario: struct Parent, struct Child1, struct Child2.

struct Parent
    method print takes nothing returns nothing
        call BJDebugMsg("Hi")
    endmethod
endstruct

struct Child1 extends Parent
endstruct

struct Child2 extends Parent
endstruct

function Test takes nothing returns nothing
    local Parent p

    if GetRandomInt(0, 1) == 0 then
        set p = Child1.create()
    else
        set p = Child2.create()
    endif

    // anyway to check if p holds an instance of Child1 or Child2?
endfunction

And for the above scenario, would calling [ljass]p.print()[/ljass] result in an error?

Thanks.

 

[Dirac]

I'm almost certain that child structs have no allocation methods and take instead the parent's methods.
I advise you to avoid struct inheritance as it takes you nowhere plus you can't extend structs to other structs that extend array (which is really stupid)

 

[Bribe]

1. Yes it is legal since Parent and Child share the same allocators.

2. [ljass]if p.getType() == Child1.typeid then[/ljass]

 

[lep]

http://wc3c.net/vexorian/jasshelpermanual.html#extendstruct

1. Yes it is technically legal but since Parent and Child do not share the same allocators this is going to cause errors for you.

Uhm? They do.

//Generated allocator of Parent
function s__Parent__allocate takes nothing returns integer
 local integer this=si__Parent_F
    if (this!=0) then
        set si__Parent_F=si__Parent_V[this]
    else
        set si__Parent_I=si__Parent_I+1
        set this=si__Parent_I
    endif
    if (this>8190) then
        return 0
    endif

    set si__Parent_type[this]=1
    set si__Parent_V[this]=-1
 return this
endfunction

//Generated allocator of Child2
function s__Child2__allocate takes nothing returns integer
 local integer this=s__Parent__allocate()
 local integer kthis
    if(this==0) then
        return 0
    endif
    set si__Parent_type[this]=3
    set kthis=this

 return this
endfunction


//Generated allocator of Child1
function s__Child1__allocate takes nothing returns integer
 local integer this=s__Parent__allocate()
 local integer kthis
    if(this==0) then
        return 0
    endif
    set si__Parent_type[this]=2
    set kthis=this

 return this
endfunction

But yeah, just read the [...] manual.

 

[Bribe]

lep, you replied too quickly. I edited my post after I saw that child way extending parent.

 

[Ayanami]

So practically, this means Parent, Child1, Child2 all together can only have 8190 instances? That's kinda lame.

 

[Bribe]

struct parent[200000]

Of course this adds plenty of KB size to your map.

 

[Dirac]

So practically, this means Parent, Child1, Child2 all together can only have 8190 instances? That's kinda lame.

The way i see it this is the only way it makes sense, but after reading what lep posted i find struct extensions to other structs even more stupid.
There's always a way to avoid them

 

[Ayanami]

struct parent[200000]

Of course this adds plenty of KB size to your map.

Is there any downside in terms of speed when exceeding over the standard limit of 8190?

 

[Bribe]

Speed loss is going to be pretty significant.

 

[GFreak45]

could you use a struct to return integers used as the arrays for other structs instances? essentially making it 8190^2 (67076100 instances)

 

[Bribe]

First change your avatar, it gives me the creeps.

Second, not in the way you think. If you want big integers which can exceed 2^31 you can use BigInt created by Nestharus.

 

[Darthfett]

I know the question has been answered, but for questions like these, remember that you can always look at the JASSHelper Manual. http://www.wc3c.net/vexorian/jasshelpermanual.html#extendstruct

After showing a struct B that extends a struct A:

Internally, B.allocate() is actually calling A's constructor and B.destroy will also call B's deconstructor. If a base struct got a custom create method, the structs extending it will have to use it for allocate(). If the custom create method requires arguments, the allocate method for child structs will require the same arguments

There's a bit of Engrish in there, but you can pretty much get the gist of it.

 

[GFreak45]

its a hate it or love it kinda thing, think of it like trying to switch from jass to only GUI, i could see a few people doing that lol

There's a bit of Engrish in there

I love you

 

[Dirac]

GFreak45 you still have a lot to learn about structs. Here i present you this example.

struct Values
    
    integer number
    
endstruct

function Test takes nothing returns nothing
    
    local integer i = Values(6).number
    
endfunction

Is the same as

struct Values
    
    integer number
    
endstruct

function Test takes nothing returns nothing
    
    local Values someValue = Values(6) // you can just write 6 here and it would work
    
    local integer i = someValue.number
    
endfunction

 

[Ayanami]

Speed loss is going to be pretty significant.

So essentially, Inheritance and Interfaces in JASS pretty bad? I mean, it's very limited.

 

[Dirac]

Yes, to avoid interfaces use textmacros
to avoid inheritance, well, don't do it

 

[GFreak45]

whats the difference between .number/.create and all of the other .tags on the end of the set variable?

 

[tooltiperror]

> Yes, to avoid interfaces use textmacros
I recommend you do not use textmacros for inheritance

I find that multiple inheritance is a very complicated and tricky concept, and I don't use it in any language. I do, however, support reopening structs (but Jass doesn't support this) and I think modules are great. You can just make a module replace a parent class and implement it, and change a few minor details.

 

[Dirac]

> Yes, to avoid interfaces use textmacros
I recommend you do not use textmacros for inheritance

to avoid inheritance, well, don't do it

If you want a function to be passed as an argument i suggest you to make your function a textmacro and run it with the function name