Selecting the Instance of a Polymorphic VI Manually

When you place a polymorphic VI on the block diagram, the polymorphic VI defaults to the first instance subVI listed in the SubVIs listbox of the Polymorphic VI dialog box. When you create a control, indicator, or constant from the polymorphic VI terminals, the default instance determines the data type of each object.

The instance of a polymorphic VI changes automatically when you wire an input. For example, if you wire a string constant to the default value input terminal of the Read Key VI, LabVIEW selects the String instance subVI of the polymorphic VI and the value output terminal changes to a string data type. If you select an instance of a polymorphic VI manually, the polymorphic VI does not behave as a polymorphic VI because it accepts only the data types of the instance you specify.

Complete the following steps to select an instance of a polymorphic VI manually.

  1. Place a polymorphic VI on the block diagram.
  2. Right-click the polymorphic VI.
  3. Select Select Type from the shortcut menu and select the subVI you want to act as the current instance.

To revert back to the polymorphic VI accepting all of the handled data types, select Select Type»Automatic from the shortcut menu.