PROTECTED: (Access Control)
Specifies protected member access control in a Type or Class
Syntax:
Parameters:
typename
member declarations
member declarations
declarations for fields, functions, or enumerations
Description:
Protected: indicates that member declarations following it have protected access.
Protected members are accessible only from inside a member procedure of their Type or Class, and classes which are derived from this Type or Class. Seen from inside such a member procedure, it is as if the protected member is in fact public, and that regardless of the object on which the access operator is applied.
member declarations following Protected: are protected until a different access control specifier is given, like Private: or Public:.
Members in a Type declaration are Public: by default if no member access control specifier is given.
Protected members are accessible only from inside a member procedure of their Type or Class, and classes which are derived from this Type or Class. Seen from inside such a member procedure, it is as if the protected member is in fact public, and that regardless of the object on which the access operator is applied.
member declarations following Protected: are protected until a different access control specifier is given, like Private: or Public:.
Members in a Type declaration are Public: by default if no member access control specifier is given.
Examples:
Type animal
Dim As String animalName
Protected:
Dim As Integer serialNumber
End Type
Type dog Extends animal
Dim As String masterName
Declare Sub setSerialNumber ( ByVal number As Integer )
End Type
Sub dog.setSerialNumber ( ByVal number As Integer )
'' This is OK. We're inside a member function of the derived type
This.serialNumber = number
End Sub
Dim As dog d
'' This is OK, animalName is public
d.animalName = "Buddy"
'' this would generate a compile error:
'' - serialNumber is protected and we're trying to access it outside its type and the derived type
'' d.serialNumber = 123456789
Dim As String animalName
Protected:
Dim As Integer serialNumber
End Type
Type dog Extends animal
Dim As String masterName
Declare Sub setSerialNumber ( ByVal number As Integer )
End Type
Sub dog.setSerialNumber ( ByVal number As Integer )
'' This is OK. We're inside a member function of the derived type
This.serialNumber = number
End Sub
Dim As dog d
'' This is OK, animalName is public
d.animalName = "Buddy"
'' this would generate a compile error:
'' - serialNumber is protected and we're trying to access it outside its type and the derived type
'' d.serialNumber = 123456789
' Example to illustrate the access control 'Protected' with a token provided by an admin right for an user right:
' - The 'admin_right' type extends the 'user_right' type.
' - Create directly an 'user_right' object is forbidden.
' ('default user_right.constructor' access and 'copy user_right.constructor' access are 'Protected')
' - The 'user_right' type has only the access right to get the token.
' ('user_right.token' get-property access is 'Public' and 'user_right.token' set-property access is 'protected')
' - The 'admin_right' type has the access rights to set and to get the token.
' ('admin_right.token' get-property access and 'admin_right.token' set-property access are 'Public')
'
' An 'admin_right' object is created, and then a reference of type 'user_right' to this object is defined.
' (create directly an 'user_right' object is forbidden)
Type user_right
Public:
Declare Property token () As String '' 'Public' to authorize user_right token get
Protected:
Declare Constructor () '' 'Protected' to forbid user_right object default-construction
Declare Constructor (ByRef u As user_right) '' 'Protected' to forbid user_right object copy-construction
Declare Property token (ByRef s As String) '' 'Protected' to forbid user_right token set
Private:
Dim As String user_right_token '' 'Private' to forbid access from outside user_right
End Type
Constructor user_right () '' Default-constructor
End Constructor
Constructor user_right (ByRef u As user_right) '' Protected copy-constructor
This.user_right_token = u.user_right_token
End Constructor
Property user_right.token () As String '' Public property user_right token get
Return This.user_right_token
End Property
Property user_right.token (ByRef s As String) '' Protected property user_right token set
This.user_right_token = s
End Property
Type admin_right Extends user_right
Public:
Declare Property token () As String '' 'Public' to authorize admin_right token get
Declare Property token (ByRef s As String) '' 'Public' to authorize admin_right token set
End Type
Property admin_right.token () As String '' Public property admin_right token get
Return Base.token '' 'Base.' to access to the base type property shadowed by this property name
End Property
Property admin_right.token (ByRef s As String) '' Public property admin_right token set
Base.token = s '' 'Base.' to access to the base type property shadowed by this property name
End Property
Dim As admin_right ar '' Create an admin_right type object 'ar'
ar.token = "fxm123456789" '' admin_right set the token for user_right
Print "'" & ar.token & "'" '' admin_right get the user_right token
Print
Dim ByRef As user_right ur = ar '' Create a user_right type reference 'ur' to the 'ar' instance of admin_right type
Print "'" & ur.token & "'" '' user_right get its token
'ur.token = "fxm0" '' Error: Illegal member access, USER_RIGHT.TOKEN.property.set (user_right cannot set its token)
'Dim As user_right ur1 '' Error: The default constructor has no public access
'Dim As user_right ur2 = ar '' Error: Constructor has no public access
Sleep
' - The 'admin_right' type extends the 'user_right' type.
' - Create directly an 'user_right' object is forbidden.
' ('default user_right.constructor' access and 'copy user_right.constructor' access are 'Protected')
' - The 'user_right' type has only the access right to get the token.
' ('user_right.token' get-property access is 'Public' and 'user_right.token' set-property access is 'protected')
' - The 'admin_right' type has the access rights to set and to get the token.
' ('admin_right.token' get-property access and 'admin_right.token' set-property access are 'Public')
'
' An 'admin_right' object is created, and then a reference of type 'user_right' to this object is defined.
' (create directly an 'user_right' object is forbidden)
Type user_right
Public:
Declare Property token () As String '' 'Public' to authorize user_right token get
Protected:
Declare Constructor () '' 'Protected' to forbid user_right object default-construction
Declare Constructor (ByRef u As user_right) '' 'Protected' to forbid user_right object copy-construction
Declare Property token (ByRef s As String) '' 'Protected' to forbid user_right token set
Private:
Dim As String user_right_token '' 'Private' to forbid access from outside user_right
End Type
Constructor user_right () '' Default-constructor
End Constructor
Constructor user_right (ByRef u As user_right) '' Protected copy-constructor
This.user_right_token = u.user_right_token
End Constructor
Property user_right.token () As String '' Public property user_right token get
Return This.user_right_token
End Property
Property user_right.token (ByRef s As String) '' Protected property user_right token set
This.user_right_token = s
End Property
Type admin_right Extends user_right
Public:
Declare Property token () As String '' 'Public' to authorize admin_right token get
Declare Property token (ByRef s As String) '' 'Public' to authorize admin_right token set
End Type
Property admin_right.token () As String '' Public property admin_right token get
Return Base.token '' 'Base.' to access to the base type property shadowed by this property name
End Property
Property admin_right.token (ByRef s As String) '' Public property admin_right token set
Base.token = s '' 'Base.' to access to the base type property shadowed by this property name
End Property
Dim As admin_right ar '' Create an admin_right type object 'ar'
ar.token = "fxm123456789" '' admin_right set the token for user_right
Print "'" & ar.token & "'" '' admin_right get the user_right token
Dim ByRef As user_right ur = ar '' Create a user_right type reference 'ur' to the 'ar' instance of admin_right type
Print "'" & ur.token & "'" '' user_right get its token
'ur.token = "fxm0" '' Error: Illegal member access, USER_RIGHT.TOKEN.property.set (user_right cannot set its token)
'Dim As user_right ur1 '' Error: The default constructor has no public access
'Dim As user_right ur2 = ar '' Error: Constructor has no public access
Sleep
Dialect Differences:
- Available only in the -lang fb dialect.
Differences from QB:
- New to FreeBASIC
See also:
Back to User Defined Types
