In OOP languages, members of a class have a specific scope that indicates visibility. Standard visibility includes private, protected, and public. Private members are usable by the defining class only (fully encapsulated). They are invisible outside of the class except by friendly classes.
Protected members are usable by the defining class and descendant classes only (plus friendly classes). Public members are usable wherever its class can be referenced.
Languages Focus: Member Visibility
Traditional member visibility specifiers for fully OOP languages are private, protected, and public. Many modern OOP languages implement additional member visibilities.
Additional member modifiers are documented under the Member Modifiers topic.
Delphi Prism Class Member Visibility Levels
In Prism, you specify each class and each class member's visibility with a Class Member Visibility Level preceding the return type. Like Delphi, you group member declarations as part of defining the interface for a class in the Interface section of a unit.
Unlike Delphi, Prism supports a traditional OO approach to member visibility with additional .Net type assembly visibility. For example, private members are truly private to the class they are declared in. In Delphi for Win32, you use strict private for true traditional private visibility.
Prism also supports assembly and protected and assembly or protected which modify the visibility of protected members to include only descendants in the same assembly (and) or publicly accessible from assembly and descendant only outside (or). OO purist might object to assembly and protected and assembly or protected and I suggest you choose the traditional private, protected, and public as your first chose at least until you both fully understand them and have a specific need for them.
Yes, we get a lot of Delphi and Prism developers that "pass through" but don't stick around. Not sure why, but that's the reality. I was hoping over the years as the content got better and better that more developers would "stick" around. We do have quite a few that visit from time to time but only a few dozen that visit more than once a week.
The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.
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