Multi-Value List Controls

We often use multi-value parameters in our automation projects as they are a way to offer options for your end user to select from.  Usually you, as the developer, will want to limit these options to what’s available, either due to selections already made or other constraints.  In this post, we’ll describe how to control values for one option based upon another selection.

Have a look at the User Interface (UI) shown below for a conveyor design by Salt Automation.

When the end user selects a Duty Cycle of Heavy, the Motor Selection options should be 7-1/2 or 5 hp, as shown in the image.  But, what if the options need to change when the end user selects a Duty Cycle of Light, to either 2 or 1 hp?

Let’s take a look at how we can accomplish this.  We can set the value options for the Duty Cycle parameter in either the Parameters dialog box via traditional methods or we can set it via iLogic code, using MultiValue.SetList.

The scheme for the MultiValue.SetList is:

    MultiValue.SetList("parameter name", "value 1", "value 2", "value 3")

In our example, it would look like this:

    MultiValue.SetList("Duty_Cycle", "Heavy", "Light")

The benefits to setting the value options in code versus the traditional method are that you can set the order in which you want them displayed but more importantly, you modify the value options at run-time through your code.

Let’s look at how we can modify the value options of our Motor Selection parameter at run-time.  We’ll do this using the Case structure.  This could also be done with an If Then statement.

    Select Case Duty_Cycle

        Case "Heavy"

            MultiValue.SetList("Motor_Selection", "7.5 hp", "5 hp")

        Case "Light"

            MultiValue.SetList("Motor_Selection", "2 hp", "1 hp")

    End Select

The code above will set the Motor Selection options based up on the selection of the Duty Cycle parameter.

The entire code is listed below.  I am also setting the ValueOptions, which will be covered later.

' Set multi-value options

    MultiValue.SetValueOptions(True, DefaultIndex := 0)

    MultiValue.SetList("Duty_Cycle", "Heavy", "Light")

' Set Motor Selection based on Duty Cycle

    Select Case Duty_Cycle

        Case "Heavy"

            MultiValue.SetList("Motor_Selection", "7.5 hp", "5 hp")

        Case "Light"

            MultiValue.SetList("Motor_Selection", "2 hp", "1 hp")

    End Select

“Don’t worry if it doesn’t work right. If everything did, you’d be out of a job.” ~ Mosher’s Law of Software Engineering

Thanks,
Randy