Responding to a Button

Category: User Interface

Problem

You want to do something when the user clicks on a button.

Ingredients

ButtonControl, Controller, FieldControl, StaticControl, Alert

Recipe

Enter this in a library (e.g. mylib) as My_Button:

Controller
    {
    Controls:
        (Vert
            (Static 'Enter your name')
            Field
            (Button Hello)
            )
    On_Hello()
        {
        Alert("Hello " $ .Vert.Field.Get())
        }
    }

You can then run it directly from Library View or from the WorkSpace with:

My_Button()

or:

Window(My_Button)

Controls like Button use .Send to send "messages" to their Controller. To handle/respond to these messages you have to create a Controller and within it, define a method corresponding to the message that the control is Send'ing. In this case, ButtonControl sends a message of "On_" $ button-name and our button is called "Hello" so our method is "On_Hello". In this example, the On_Hello method simply displays an Alert - but it could, of course, do other things.

Discussion

The example code also demonstrates one way to access the contents of a field control - a better alternative if you have a lot of fields is to use a RecordControl.

If you only want your controller to catch some messages and to pass the rest on to any containing controller, use PassthruController instead of Controller.

See Also

Using RecordControl, Determining the Source of Messages