在Haxe中，如何在函数中传递Enum值，然后在函数内将它们转换为String？

Question

I can't seem to get this working, but I'd be surprised if it wasn't possible in Haxe.

I'm trying to pass a couple of Enum values defined in my game to a function, so that it can then concatenate them as String types and pass that to other functions.

Example:

// In a general Entity class:
public override function kill():Void {
    messages.dispatchCombined(entityType, ListMessages.KILLED);

    super.kill();
}

And in my Messages.hx class:

package common;

import msignal.Signal.Signal1;

/**
 * A Message / Event class using Signals bound to String names.
 * @author Pierre Chamberlain
 */
class Messages{
    var _messages:MessagesDef;

    public function new() {
        _messages = new MessagesDef();
    }

    public function add(pType:String, pCallback:FuncDef) {
        if (_messages[pType] == null) {
            _messages[pType] = new Signal1<Dynamic>();
        }

        var signals = _messages[pType];
        signals.add( pCallback );
    }

    public function dispatch(pType:String, pArg:Dynamic):Bool {
        var signals = _messages[pType];
        if (signals == null) return false;
        signals.dispatch(pArg);
        return true;
    }

    //Compiler doesn't like passing enums :(
    public inline function addCombined(pSource:Enum, pEvent:Enum, pCallback:FuncDef) {
        add( combine(pSource, pEvent), pCallback );
    }

    public inline function dispatchCombined(pSource:Enum, pEvent:Enum, pArg:Dynamic):Bool {
        return dispatch( combine(pSource, pEvent), pArg);
    }

    //How can I just pass the enum "names" as strings?
    static inline function combine(a:Enum, b:Enum):String {
        return String(a) + ":" + String(b);
    }
}


typedef MessagesDef = Map<String, Signal1<Dynamic>>;
typedef FuncDef = Dynamic->Void;

Note how addCombined , dispatchCombined and combine expect an "Enum" type, but in this case I'm not sure if Haxe actually expects the entire Enum "class" to be passed (ie: ListMessages instead of ListMessages.KILLED ) or if a value should work. Anyways, compiler doesn't like it - so I'm assuming another special Type has to be used.

Is there another way to go about passing enums and resolving them to strings?

Answer 1

I think you need EnumValue as parameter type (if it is only for enum values), and use Std.String to convert to String values.

static inline function combine(a:EnumValue, b:EnumValue):String {
    return Std.string(a) + ":" + Std.string(b);
}

Of course that can be written smaller using String interpolation :

static inline function combine(a:EnumValue, b:EnumValue):String {
    return '$a:$b';
}

Of course that can be 'more dynamic' using type parameters :

static inline function combine<A, B>(a:A, b:B):String {
    return '$a:$b';
}

There is totally no need to use Dynamic as suggested. If you use Dynamic, you basically turn off the type system .

live example:
http://try.haxe.org/#a8844

Answer 2

Use Dynamic instead of Enum or pass them as Strings right away since you can always convert to enum from String if you need it later.

Anyway pass the enum as enum:Dynamic and then call Std.string(enum);

EDIT: Using EnumValue is definitely better approach than Dynamic, I use Dynamic in these functions because I send more than just Enums there and I am not worried about type safety in that case.