Hello,

Why a attribute cannot be abstract ?
How can I force the redefinition of an attribute if the class inherits from abstract class ?

Example:
----------------

abstract class A
{
// Error: variable attr cannot be abstract
protected abstract int attr;
}

class B : A
{
protected override int attr = 10;
}

On Tuesday, 17 May 2016 at 16:52:01 UTC, Lucien wrote:
> Why a attribute cannot be abstract ?

Because it cannot be virtual and cannot be overridden. This is different than Python, but in line with other C-style languages (and the lower level implementation)

Use a property function instead to achieve this.

abstract class A
{
  protected @property abstract int attr(); // a getter for attr
  protected @property abstract attr(int); // a setter for attr, if desired
}

class B : A
{
   override @property int attr() { return 0; } // implementation
}

On Tuesday, 17 May 2016 at 16:58:30 UTC, Adam D. Ruppe wrote:
> On Tuesday, 17 May 2016 at 16:52:01 UTC, Lucien wrote:
>> Why a attribute cannot be abstract ?
>
> Because it cannot be virtual and cannot be overridden. This is different than Python, but in line with other C-style languages (and the lower level implementation)
>
> Use a property function instead to achieve this.
>
> abstract class A
> {
>   protected @property abstract int attr(); // a getter for attr
>   protected @property abstract attr(int); // a setter for attr, if desired
> }
>
> class B : A
> {
>    override @property int attr() { return 0; } // implementation
> }

ok, thank you.