Is it possible somehow..?

BlitzMax Forums/BlitzMax Programming/Is it possible somehow..?

Hardcoal

(Posted 2016) [#1]


Global Suzan:xxx=new xxx
Global John:xxx=new xxx

Global Ellen:xxx

Global Goerge:xxx=Ellen
Global Tony:xxx=Ellen

Ellen=Suzan

'George and Tony should change.. to Suzan

Ellen=John

'George and Tony should change.. to John

Type xxx
 '...
End Type

Is it possible somehow that when I change Ellen Value, George and Tony will be updated?

Im looking for a way to make George and Tony to be the pointers of Ellen..
So when Ellen is changing then those objects will change too..
So lets say if I have 100 Pointers towards Ellen, I wont need to change them one by one.

Tnx

Cocopino

(Posted 2016) [#2]

I'm not sure what you're trying to achieve here...
If all objects should always be identical to Ellen, why have all these other objects at all?

Chapman7

(Posted 2016) [#3]

This is what happens:

SuperStrict

Type Person
	Field Name:String
	
	Method SayName()
		Print Name
	EndMethod
EndType


Local Suzan:Person = New Person
Suzan.Name = "Suzan"

Local Ellen:Person = New Person
Ellen.Name = "Ellen"


Local George:Person = Ellen



Print George.Name

Ellen.Name = "test"

Print George.Name

'When Ellen = Suzan, George becomes his own person
'and Ellen no longer affects him, I think it's
'due to a memory address change but I have no clue
Ellen = Suzan

Print George.Name

Your best bet is something like:

SuperStrict

Type Person
	Field Name:String
	
	Method SayName()
		Print Name
	EndMethod
	
	Method Copy(Peer:Person)
		Self.Name = Peer.Name
		'Copy any and all fields
	EndMethod
EndType


Local Suzan:Person = New Person
Suzan.Name = "Suzan"

Local Ellen:Person = New Person
Ellen.Name = "Ellen"


Local George:Person = Ellen



Print George.Name

Ellen.Name = "test"

Print George.Name

'When Ellen = Suzan, George becomes his own person
'and Ellen no longer affects him, I think it's
'due to a memory address change but I have no clue
'Ellen = Suzan
Ellen.Copy(Suzan)

Print George.Name

Cocopino

(Posted 2016) [#4]

When George, Suzan, etc are separately declared as variables, they get their own memory allocated to them so they are not affected by anything unless you code them to do so.

Suzan = Ellen

This only means to copy the CURRENT field values from Ellen to Suzan ONCE, not making it a pointer.

But if George, Suzan, etc objects should act like pointers, they should always be exactly equal to Ellen in which case I don't see their purpose in the first place.

col	(Posted 2016) [#5]

There is varptr but it only works on non-objects. You'll have to find another solution. You could work some carefully thought out c magic and use a function to assign and unassign the variables. I suggest not to do that though, and bite the bullet to iterate through a collection.

Hardcoal

(Posted 2016) [#6]

My attempt was is to save speed..
I think what I desire is either impossible
Or it doesn't make sense.
But i had to ask..
I will rethink my options
And see what to do
Tnx

Silver_Knee

(Posted 2016) [#7]

You can use an array or self defined container to hold the reference:

Local container:TString[] = ["Foo"]

Local a:TString[]=container
Local b:TString[]=container


a[0]="Bar"
DebogLog b[0] 'Bar

This pattern is used in Java for anonymous inline functions so they can change the contents of a variable.

Derron

(Posted 2016) [#8]

Similar to Silver_Knee's approach I would throw in:

- create a TMap containing: KEY->OBJECT (this ensures, that each key is only used once - compared to a TList)

- now just add each of the objects to the map (map.insert("Suzan", Suzan) - and so on)

- "Goerge" is then not an object of type "xxx" but becomes a string, containing the key of the referenced object (so Global Goerge:string = "Suzan")

- objects are then retrieved via xxx(map.ValueForKey(key))

This way you decouple connections between variables: once you remove the value behind the key "Suzan" from the map, all other variables ("Goerge" and so on) will result in invalid ("null") variables, even if there referenced key is still set to "Suzan". So once you add "Suzan" back, they would result in valid objects again.

bye
Ron

Hardcoal

(Posted 2016) [#9]

Ok, Great, Tnx guys for the help..
Ill see what I can do with that.

Matty

(Posted 2016) [#10]

Why have George and Tony? They are redundant since they are also Ellen initially?

Derron

(Posted 2016) [#11]

@ Matty
I think the intention is, to get a general approach to handle multiple references to an object which auto-update on their own.

Think of this:

File 1:
import "File2.bmx"
Import "File3.bmx"

'create cars
'....

car1 = null

if car2.name = "Car1" then print "object still existing"



File 2:
Import "car.bmx"
Global car1:TCar = new TCar.Init("Car1")

File 3 (File 2 does not know what happens in File 3)
Import "file1.bmx"
global car2:TCar = car1

When now decoupling the real object reference by using eg. a "key->value"-TMap, you just have "car2" being a key with the value "Car1".
The real "decoupling" happens, because you then use "Getters" ("GetCar(key)") instead of using the object directly.

I think if you imagine a "Sprite"-type having an "image:TImage"-Field, you will understand what I am talking about. What happens, if multiple "Sprites" share the same "image". What happens then, if you adjust the image in one of the sprites. If you want to have all of them keep using the same image (the new one) you cannot do it this way - you either have to wrap the object (the TImage-property) in another container ("TSpriteImage") and adjust the containers properties ("TSpriteImage.SetImage(bla)") or you indirectly reference them by a unique key ("GUID", "ImageURI" or whatever).

bye
Ron