Static method call on inheritance

[Alexander Popov]

Hi!

How can I get this class in static method? Class of child in parent static method.

Example of code

Thanks.

[Mark Knol]

You cannot acces 'this' in a static method. Because 'this' refers to a instance and statics are global so to say.

So either you have to pass an instance of the class to your method, or you have to remove the 'static' keyword.

[Alexander Popov]

Okay, another example: https://gist.github.com/AlexWayfer/7848b5560119fda01aac3999a4bf624b

So, I can not do one of these in Haxe?

[Anton Nesterov]

You're approaching the problem from a wrong angle. Static variables are only existing in a class that's declaring them, they aren't accessable from other classes. What you really need is build macro (haxe unique feature).

In some other languages you can find functionality called "mixin". Haxe doesn't have that out of the box, but you can add it with @:autoBuild macro. In your parent class you want to create a macro method, that will be called at compile time for every child class. Then this macro adds a method you need into every child class.

Now some code:

TestMacro.hx file first:

import haxe.macro.Context;
import haxe.macro.Expr;

class TestMacro {
    macro static public function build_some_method() : Array<Field> {
        var fields = Context.getBuildFields();
       
        // you can't generate methods, but you can generate class
        // and copy it's method to destination class
        var c = macro class X {
            static public function some_method() {
                return Animal.some_method_internal(some_var);
            }
        };
        // extract method we want
        var m = Lambda.find(c.fields, function(f) return f.name == "some_method");
        // insert into target class
        fields.push(m);
        // return modified field set
        return fields;
    }
}

And then is your animals source code:

@:autoBuild(TestMacro.build_some_method()) //<< invoke macro for child classes
class Animal {

...

  static private function some_method_internal(value : String) { //<< changed to internal private method with parameter passed from macro generated fn
    // some needed magic
  }

...  

среда, 29 июня 2016 г., 3:44:07 UTC+3 пользователь Alexander Popov написал: