CODEWITHSUNDEEP
reflectionhaxe
George Vinokhodov
George Vinokhodov

Reputation: 336

Haxe get function parameter type

I have haxe code like this:

var fn:String->Int = function(s:String):Int{
    return 1;
}

getParameterType(fn,1);//Should return String as it is first parameter of fn

what should function getParameterType code look like?

Upvotes: 1

Views: 1097

Answers (1)

Jason O'Neil
Jason O'Neil

Reputation: 6008

The Haxe Reflection APIs can be found here: Reflect and Type.

Looking through them, there doesn't seem to be any way to check the types of arguments on functions, probably because this information isn't available at runtime on many of the platforms. Javascript for instance is loosely typed, and the information you are looking for is not included by default.

So you have three options:

  1. Use RTTI (Run Time Type Info). If a class is marked with @:rtti metadata (in Haxe 3, or if it implements haxe.rtti.Infos in Haxe 2), then information about that class, including the types of function parameters, is available in Xml format at run time. You will have to look at the Xml to figure out what the argument is. This will only work for functions which are attached to classes though, it won't work for anonymous functions.

  2. Use macros. This is outside the scope of my answer, but maybe ask on the Haxe mailing list if you need help :) If the argument type is known at compile time, it can be made known to macros, and you can probably save that information back somewhere so it is available at run time.

  3. Figure out another usage that doesn't require you to know the type :)

Of course, if you only need the information at compile-time, not at run-time, you can do: $type(fn) anywhere in your code and when you compile it will let you know the exact type signature of "fn".

Upvotes: 5

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