Member Access Rights


Restricting member access to certain parts of code.

Overview
Public members
Protected members
Private members
Constructors and destructors

Overview
All members of a Type or Class - including member data, procedures, constants, etc. - belong in one of three different classifications, each with its own rules dictating where in code they may be accessed, or referred to. These rules are called access rights. There are public, protected and private members, and they are declared in a Type or Class definition following a Public, Protected or Private label, respectively.

By default, that is, without an access classification label, members of a Type are public, and members of a Class are private.

Public members
Public members can be referred to from anywhere; they are accessible from, for example, member procedures or module-level code or procedures.

Protected members
Protected members can only be accessed from member procedures of the Type or Class they are declared in, or member procedures of a derived Type or Class. They are not accessible to outside code.

Private members
Private members can only be accessed from member procedures of the Type or Class they are declared in. They are not accessible to outside code or member procedures from a derived Type or Class.

Constructors and destructors
Constructors and destructors follow the same rules as any other member. When public, objects can be instantiated and destroyed from anywhere in code. When protected, objects can be instantiated and destroyed only from member procedures of their Type or Class or a derived Type or Class. Private constructors and destructors restrict object instantiation solely to member procedures of their Type or Class.

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