Variable variable name in twig

Question

I have a twig macro for creating a combo box form element like this :

{% macro select(name, label, choices, help, value) %}
<div class="control-group">
    <label class="control-label" for="{{ name }}">{{ label }}</label>
    <div class="controls">
        {% for choice in choices %}
            {% if value is not empty and value == choice.id %}
                <option value="{{ choice.id }}" selected="selected">{{ choice.code }} - {{ choice.name }}</option>
            {% else %}
                <option value="{{ choice.id }}">{{ choice.name }}</option>
            {% endif %}
        {% endfor %}
        <p class="help-block">{{ help }}</p>
    </div>
</div>
{% endmacro %}

As you can see, it's not very flexible because I can only use objects with id and name field as the option value and label. Before migrating to twig, I use this PHP function :

function form_select($name, $label, $choices, $keycol, $valcol, $value=null, $help=null)
{ ?>
<div class="control-group">
    <label class="control-label" for="<?php echo $name; ?>"><?php echo $label; ?></label>
    <div class="controls">
        <select name="<?php echo $name; ?>" class="span7" id="<?php echo $name; ?>">
            <?php foreach ($choices as $choice) : ?>
                <option value="<?php echo $choice->$keycol; ?>" <?php if ($choice->$keycol == $value) echo "selected"; ?>>
                    <?php echo $choice->$valcol; ?>
                </option>
            <?php endforeach; ?>
        </select>
        <p class="help-block"><?php echo $help; ?></p>
    </div>
</div>
<?php }

With this function I can send arbitrary objects to the function and use it as the option value and label by passing the field name to the function ($keycol and $valcol) and accessing them via PHP's variable variable name feature ($choice->$keycol and $choice->$valcol).

Is there anyway I can recreate this function as a twig macro?

Answer 1

The attribute function does this : http://twig.sensiolabs.org/doc/functions/attribute.html

{{ attribute(choice, valCol) }}