Re: Introduction to traits (and __traits)

[Joseph Rushton Wakeling]

On 30/08/13 21:40, Benjamin Thaut wrote:
You need to put it into a static if, otherwise the compiler will continue
semantic checks on the second part of the expression. E.g.
template isGraph(G)
{
   static if(__traits(hasMember, G, "directed"))
     enum bool isGraph = isBoolean!(typeof(G.directed));
   else
     enum bool isGraph = false;
}

Ahh, right, thanks. :-)

Is there a recommended way for handling the case where there are many such 
members -- say about 10 or more?  The static if's could become very highly 
nested with this approach.  I suppose I could go through like this:

    static if(!__traits(hasMember, G, "one"))
        enum bool isGraph = false;
    else static if(!__traits(hasMember, G, "two"))
        enum bool isGraph = false;
    else static if ...
        ...
    else
    {
        // Now I know all the members exist and I can
        // start checking out their properties ...
    }