Re: How to create mixin template and pass name of a variable?

[Andrej Mitrovic]

On Friday, 2 August 2013 at 11:37:27 UTC, Bosak wrote:
I want to create a mixin template such that:
mixin template ArgNull(alias arg, string name)
{
    if(arg is null)
        throw new Exception(name~" cannot be null.");
}

But is there a way to do that with only one template argument. 
And then use it like:

string text = null;
mixin ArgNull!(text);

And the above mixin to make:

if(text is null)
    throw new Exception("text cannot be null.");

Note that template mixins cannot inject arbitrary code, they can 
only inject declarations. You can use '__traits(identifier, 
symbol)' on an alias parameter to retrieve the symbol name, for 
example:

-----
mixin template ArgNull(alias arg)
{
    void test()
    {
        if (arg is null)
            throw new Exception(__traits(identifier, arg) ~ " 
cannot be null.");
    }
}

string text = null;
mixin ArgNull!text;

void main()
{
    test();
}
-----