Controlling access for instance variables

Instance variables have access settings that provide control over how other objects' scripts access them.

You can specify that a variable is:

  • Public

    Accessible to any other object

  • Protected

    Accessible only in scripts for the object and its descendants

  • Private

    Accessible in scripts for the object only

For example:

public integer ii_currentvalue
CONSTANT public integer WARPFACTOR = 1.2
protected string is_starship

// Private values used in internal calculations
private integer ii_maxrpm
private integer ii_minrpm

You can further qualify access to public and protected variables with the modifiers PRIVATEREAD, PRIVATEWRITE, PROTECTEDREAD, or PROTECTEDWRITE:

public privatewrite ii_averagerpm

Private variables for encapsulation

One use of access settings is to keep other scripts from changing a variable when they should not. You can use PRIVATE or PUBLIC PRIVATEWRITE to keep the variable from being changed directly. You might write public functions to provide validation before changing the variable.

Private variables allow you to encapsulate an object's functionality. This technique means that an object's data and code are part of the object itself and the object determines the interface it presents to other objects.

If you generate a component from a custom class user object, you can choose to expose its instance variables in the component's interface, but private and protected instance variables are never exposed.

For more information

For more about access settings, see Declarations in PowerScript Reference.

For more about encapsulation, see Selected Object-Oriented Programming Topics.