On Thu, Apr 15, 2021 at 08:56:18PM +0000, mw via Digitalmars-d-learn wrote:
[...]
> of course, one can manually dispatch:
>
> if (userInputString == "cat") createCat();
> else if (userInputString == "dog") createDog();
> ...
>
> but this this tedious.
-------------------
// Disclaimer: this is proof of concept, I didn't actually run this yet
class Animal {}
class Cat : Animal {}
class Dog : Animal {}
alias SupportedTypes = AliasSeq!(Cat, Dog, /* whatever else you want here */);
string userInputString = ...;
Animal result;
SW: switch (userInputString) {
static foreach (T; SupportedTypes) {
case T.stringof:
result = new T;
break SW;
}
default:
throw new Exception("Unknown object type");
}
-------------------
> I have a similar question: how to dynamically use user's input string
> as function name can call it? suppose the function has no argument.
Same idea:
-------------------
// Disclaimer: this is proof of concept, I didn't actually run this yet
struct Dispatcher {
void bark() { ... }
void meow() { ... }
void moo() { ... }
... // whatever else you want here
}
Dispatcher disp;
string userInputString = ...;
SW: switch (userInputString) {
static foreach (fieldName; __traits(allMembers, disp)) {
static if (is(typeof(__traits(getMember, disp, fieldName))
== function)
{
case fieldName:
__traits(getMember, disp, fieldName)();
break SW;
}
}
}
-------------------
Basically, the idea is to obtain a list of types/methods/whatever
somehow (either by explicitly listing instances, or via compile-time
introspection), then statically generate switch cases from it. You can
eliminate many kinds of boilerplate using this little trick.
T
--
Береги платье снову, а здоровье смолоду.
