Re: Suggested Change to Contract Syntax

[jmh530 via Digitalmars-d]

On Friday, 11 March 2016 at 01:45:36 UTC, Jonathan M Davis wrote:

Sure, but if you're not using in/out contracts with a class, 
you're not going to see how they interact with inheritance. To 
mimic what they do, you'd have to duplicate the base class 
contracts in the derived class and make sure that you ||ed the 
in contracts correctly and &&ed the out contracts correctly, 
which isn't very maintainable.

- Jonathan M Davis

If I'm understanding you correctly, you could still get the same 
behavior with something like below (though it isn't exactly right 
since Base.foo's in block would technically have a funky rule 
applied to it).

After playing around with your example, I'm finding in/out blocks 
on derived classes to be tricky. I think I'm going to try to 
avoid putting myself in a situation where I would screw something 
up.

import core.exception;
import std.exception;

class Base
{
        void baseCheck(int i)
        {
                assert(i % 2 == 0, "base out failed");
        }

    int foo(int i)
    {
                assert(i > 0 && i < 10, "base in failed");
                scope(exit) baseCheck(i);

        return i;
    }
}

class Derived : Base
{
    override int foo(int i)
        {
                scope(exit) baseCheck(i);
                
        assert(i < 50, "derived in failed");
                scope(exit) assert(i % 3 == 0, "derived out failed");

        return i;
    }
}