haxe：基于变量值的宏验证内的不同代码

Question

This works ok:

//somewhere in Foo:
static function bar(arg:StringMap<Dynamic>) {trace(arg.toString())}
...
//somewhere in build macro:
var myArr = [macro "k1"=>100, macro "k2"=>200, macro "k3"=>300];
var newExpr = macro {
    Foo.bar($a{myArr});
}

But in reality sometimes myArr.length == 0 and this gives compilation error:

Array<Unknown<0>> should be haxe.ds.StringMap<Dynamic>

So I should replace $a{myArr} with null or new StringMap() if the length of myArr is zero, but how can I do this?

Currently I did this:

var newExpr = myArr.length == 0 ? 
    macro {
        Foo.bar(null);
    } : macro {        
        Foo.bar($a{myArr});
    };

But in reality the code in macro is bigger...

Answer 1

您可以使用${}在宏验证内运行条件

var newExpr = macro Foo.bar(${myArr.length == 0 ? macro null : macro $a{myArr}});

Answer 2

The solution is very easy:

var myArr = [macro "k1"=>100, macro "k2"=>200, macro "k3"=>300];
...
var arrExpr = myArr.length == 0 ? macro new Map<String, Dynamic>() : macro $a {myArr};
var newExpr = macro {
    Foo.bar($arrExpr);
}