I know there is mutable variables, but what is a mutable method?

Error message says "mutable method project.mariadb.connector.ver2p1.resultset.ResultSetColumn.info is not callable using a const object".

On Friday, 22 May 2015 at 12:12:46 UTC, tcak wrote:
> I know there is mutable variables, but what is a mutable method?
>
> Error message says "mutable method project.mariadb.connector.ver2p1.resultset.ResultSetColumn.info is not callable using a const object".

The method that can change the state of the object.
This kind of error says that you try to call non-const method on const object, which is prohibited. You can call only the methods marked as const on the const object.

On 5/22/15 8:12 AM, tcak wrote:
> I know there is mutable variables, but what is a mutable method?
>
> Error message says "mutable method
> project.mariadb.connector.ver2p1.resultset.ResultSetColumn.info is not
> callable using a const object".

English grammar nit: I would say mutating instead of mutable.

-Steve

On Friday, May 22, 2015 12:12:45 tcak via Digitalmars-d-learn wrote:
> I know there is mutable variables, but what is a mutable method?
>
> Error message says "mutable method project.mariadb.connector.ver2p1.resultset.ResultSetColumn.info is not callable using a const object".

It's a method / member function which is not const or immutable. e.g.

struct MyStruct
{
    void foo() {}  // This method is mutable
    void bar() const {}
    void baz() immutable {}
}

What it's really indicating is the constness of the object's this point is inside the function. So, you can only call a mutable method on a mutable object, because otherwise, you'd be converting a const or immutable reference or pointer to mutable, which would violate the type system. mutable and immutable can be converted to const, but mutable and const can't be converted to immutable, and const and immutable can't be converted to mutable.

So, in your case, it sounds like you're trying to call a mutable method on a const object, which won't work. The method needs to be const, since the object is const.

- Jonathan M Davis