feat(dropdown): Add additional field for setting an optional reference (like in TreeView)

dropdown.go

@@ -9,8 +9,9 @@ import (
 
 // DropDownOption is one option that can be selected in a drop-down primitive.
 type DropDownOption struct {
-	text     string                                  // The text to be displayed in the drop-down.
-	selected func(index int, option *DropDownOption) // The (optional) callback for when this option was selected.
+	text      string                                  // The text to be displayed in the drop-down.
+	selected  func(index int, option *DropDownOption) // The (optional) callback for when this option was selected.
+	reference interface{}                             // An optional reference object.
 }
 
 func NewDropDownOption(text string) *DropDownOption {
@@ -34,6 +35,17 @@ func (d *DropDownOption) SetSelectedFunc(handler func(index int, option *DropDow
 	return d
 }
 
+// GetReference returns the reference object of this dropdown option.
+func (d *DropDownOption) GetReference() interface{} {
+	return d.reference
+}
+
+// SetReference allows you to store a reference of any type in this option.
+func (d *DropDownOption) SetReference(reference interface{}) *DropDownOption {
+	d.reference = reference
+	return d
+}
+
 // SetChangedFunc sets a handler which is called when the user changes the
 // drop-down's option. This handler will be called in addition and prior to
 // an option's optional individual handler. The handler is provided with the