Question

I am reimplementing a java program in D. I have used the factory pattern,
that is, from the data “myclass” “5.3 ,6,8,10”, I use reflection to call the constructor

myclass(5.3 ,6,8,10);

How can I solve the same problem in D, that is, given a class name, and the parameters
the constructor takes (only primitives), create an instance of that class by calling the constructor in the parameters?

One obvious solution is the following: Make a huge switch/case statement,
with class names as cases, and make constructor take a double[] as argument.
This is ugly, since I need to add each new class to this list.

I might enforce each class to statically add themself to some global map,
mapping class name to constructor, somehow.

Answer 1

You could have a list with helper objects. The helper objects (MiniFactory) basically have a test method and a factory method, so you can say:

for (int i=0; i<max_classes; i++) {
    MiniFactory f = factoryList[i];
    if (f.typeIsMatching(inputString))
        return f.createObject(inputArgs);
}

With some luck you can use templates to define the MiniFactories.