• Lucien (15/15) May 17 2016 Hello,
• Adam D. Ruppe (15/16) May 17 2016 Because it cannot be virtual and cannot be overridden. This is
• Lucien (2/18) May 17 2016 ok, thank you.

Lucien <lucien.perregaux gmail.com> writes:

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;
}

Adam D. Ruppe <destructionator gmail.com> writes:

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
}

Lucien <lucien.perregaux gmail.com> writes:

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.