[Gambas-user] Direct assignment to arrays of inherited classes does not work

[Tobias Boege]

On Mon, 22 Sep 2014, Julio Sanchez wrote:
> Direct assignment to arrays of inherited classes does not work
> 
> We have a class that inherits from the integer class [], we call
> SuperInteger, this is your code:
> Inherits Integer []
> 
> Public function  higher() as integer
> dim itemt as integer
> dim ihigher as integer
> 
> for each element in me
> ihigher = max (ihigher, item)
> next
> 
> return ihigher
> 
> end
> 
> 
> When I make an instance of the new :
> 
> dim test as new SuperInteger
> 
> 
> It does not work this assignment:
> test = [86, 16, 212, 1, 43, 18]
> 
> gambas3 says it's not the same type.
> Should I working? Right?
> 

No, because it is not the same type :-)

Even if B inherits A, it can be very difficult to make sense of an
assignment myB = myA because myB could reference _lots_ of other
information (which is not in the class A). What should happen to this
information in the assignment? You simply can't convert myA to the B
class.

The clean solution would be to define a static B.FromA() method which
takes an A object and returns a new B object which contains that A
object and initialises all other information appropriately.

So, you would implement

  Static Public Function FromArray(aArray As Integer[]) As SuperInteger

or something along these lines in SuperInteger. For a more concise
syntax, you may also use the _call() special method. Then you can do

  myB = SuperInteger([1, 2, 3, 4])

Regards,
Tobi

-- 
"There's an old saying: Don't change anything... ever!" -- Mr. Monk