"Quick" workaround for different named attributes in variant types

test.nim

import strformat

type
    WidgetKind = enum
        Frame, Separator, Header, Label, Button
    ButtonKind = enum
        IconButton, TextButton

type Widget* = ref object
    id*:int
    x*, y*, w*, h*:int
    case kind:WidgetKind
        of Frame, Separator:   cells*:seq[seq[int]]
        of Label, Header:      text_field*:string   # text
        of Button:
            case button_kind:ButtonKind
                of IconButton:  button_icon:int
                of TextButton:  button_text:string  # text
            hit_on_release*:bool
            is_toggle*:bool




template text*(self:Widget):string =
    assert(self.kind == Button and self.button_kind == TextButton or self.kind in [Label, Header])
    if self.kind == Label:
        self.text_field
    elif self.kind == Button and self.button_kind == TextButton:
        self.button_text

template `text=`*(self:Widget, text:string)=
    assert(self.kind == Button and self.button_kind == TextButton or self.kind in [Label, Header])
    if self.kind == Label:
        self.text_field = text
    elif self.kind == Button and self.button_kind == TextButton:
        self.button_text = text


template icon*(self:Widget):int =
    assert(self.kind == Button and self.button_kind == IconButton)
    if self.kind == Button and self.button_kind == IconButton:
        self.button_icon

template `icon=`*(self:Widget, icon:int) =
    assert(self.kind == Button and self.button_kind == IconButton)
    if self.kind == Button and self.button_kind == IconButton:
        self.button_icon = icon




proc `$`*(self:Widget):string =
    case self.kind
        of Label:   echo fmt "Label(x: {self.x}, y: {self.y}, text: {self.text_field})"
        of Button:
            case self.button_kind
                of TextButton:   echo fmt "TextButton(x: {self.x}, y: {self.y}, text: {self.button_text})"
                of IconButton:   echo fmt "IconButton(x: {self.x}, y: {self.y}, icon: {self.button_icon})"
        else: discard

proc new_widget(kind:WidgetKind, x, y, w, h:int):Widget =
    result = Widget(
        kind : kind,
        x : x,
        y : y,
        w : w,
        h : h
    )




proc new_label*(x, y:int, text:string):Widget =
    result = new_widget(Label, x, y, 0, 0)
    result.text = text

proc new_icon_button*(x, y, icon:int):Widget =
    result = new_widget(Button, x, y, 1, 1)
    result.button_kind = IconButton
    result.icon = icon
    result.hit_on_release = false
    result.is_toggle = false

proc new_text_button*(x, y:int, text:string):Widget =
    result = new_widget(Button, x, y, 1, 1)
    result.button_kind = TextButton
    result.text = text
    result.hit_on_release = false
    result.is_toggle = false




#       TESTS
# -----------------------------------------------------------------------------
var l = new_label(10, 5, "derp")
var ib = new_icon_button(10, 10, 254)
var tb = new_text_button(10, 20, "bla bla")

echo l      #  >>> Label(x:10, y:5, text: derp)
echo ib     #  >>> IconButton(x:10, y:10, icon: 254)
echo tb     #  >>> TextButton(x:10, y:20, text: bla bla)