class AbstractFormItem implements FormItem<T> {

    @Override
    public void setExpressionValue(String expressionValue) {
        this.value = null;
        this.expressionValue = expressionValue;

        appearances.values().forEach(a -> {
            a.unapply(DEFAULT);
            a.showExpression(expressionValue);
        });
        toggleExpressionSupport(expressionValue);
    }

      AbstractFormItem(String name, String label, String hint);

}