How to check if Variant not null before coerce it?

Question

I an getting from database data with Variant type. I need to check if variable have any data before coerce it.

  cargpspoint.speed = point[0].coerce!int;

if point[0] will be null I will get exception. I need to do coerce only if variable have value. There is long way with:

if(point[0].hasValue && point[0].peek!(int) !is null)

Is there any way to do it shorter? Or at last to not throw Exception if there is null inside.

https://dlang.org/phobos/std_variant.html

Answer 1

You could check whether the typeid inside is void.

import std.variant : Variant;

struct CarGPSPoint
{
    int speed;
}

void main()
{
    Variant point[] = new Variant[5];

    CarGPSPoint cargpspoint;

    if ( point[0].type != typeid(void) )
        cargpspoint.speed = point[0].coerce!int;
}

Alternatively just catch and discard the exception.

import std.variant : Variant, VariantException;

struct CarGPSPoint
{
    int speed;
}

void main()
{
    Variant point[] = new Variant[5];

    CarGPSPoint cargpspoint;

    try
        cargpspoint.speed = point[0].coerce!int;
    catch (VariantException e) {}
}