vtable.sh

#!/usr/bin/env bash
# -*- mode: shell-script; sh-shell: bash; sh-basic-offset: 4; sh-indentation: 4; coding: utf-8 -*-
# shellcheck shell=bash

set -o nounset -o errexit -o errtrace -o pipefail

readonly _NAME_FIELD='name'
readonly _ACTION_FIELD='action'

function widget:get_name() {
    local -n widget_struct_ref="${1}"

    echo "${widget_struct_ref["${_NAME_FIELD}"]}"
}

function widget:_get_action() {
    local -n widget_struct_ref="${1}"

    echo "${widget_struct_ref["${_ACTION_FIELD}"]}"
}

function widget:do_action() {
    local -n widget_struct_ref="${1}"

    local action
    action=$(widget:_get_action "${!widget_struct_ref}")
    readonly action

    "${action}" "${!widget_struct_ref}"
}

function english_widget:action() {
    local -n widget_struct_ref="${1}"

    local name
    name=$(widget:get_name "${!widget_struct_ref}")
    readonly name

    echo "Hello, ${name}!"
}

function english_widget:new() {
    local -n widget_struct_ref="${1}"
    local -r name="${2}"

    widget_struct_ref["${_NAME_FIELD}"]="${name}"
    widget_struct_ref["${_ACTION_FIELD}"]="english_widget:action"
}

function german_widget:action() {
    local -n widget_struct_ref="${1}"

    local name
    name=$(widget:get_name "${!widget_struct_ref}")
    readonly name

    echo "Guten tag, ${name}!"
}

function german_widget:new() {
    local -n widget_struct_ref="${1}"
    local -r name="${2}"

    widget_struct_ref["${_NAME_FIELD}"]="${name}"
    widget_struct_ref["${_ACTION_FIELD}"]="german_widget:action"
}

function main() {
    local -A travis_widget
    english_widget:new travis_widget "Travis"

    local -A hans_widget
    german_widget:new hans_widget "Hans"

    echo "Greeting Travis in English:"
    widget:do_action travis_widget

    echo "Greeting Hans auf Deutsch:"
    widget:do_action hans_widget
}

main