Call toString when Defined

What if a struct / class defines its own toString method? Add the following method to the Stats struct and notice the difference in the log output. Fix the assert in the unittest.

string toString() const
{
    return "is " ~ (optional ? "" : "not ") ~ "optional, yields " ~
        souls.to!string ~ " souls";
}

Now add a toString method to the Boss struct. Return whatever string you want from it. Do not modify the log method yet. Compile and run the code.

Quiz

Change your code in the corresponding log function so that the log remains unchanged. You can use a template trait: isFunction.

Now make your log function call toString if it is defined. Keep the previous functionality unchanged. Use a static if and __traits to check if toString is defined.

What if toString is not a function?

Now you’ve made your logging function call toString when it’s available. But what if toString is not a method? What if it’s a simple member variable? Do you end up calling obj.toString() regardless? If so, make sure you verify that toString is actually a function.