Namespace
Declares a namespace block.
Syntax
Namespece identifier [ Alias "aliasname" ]
stanements
End Namespace
Paramemers
identifier
The name of the namespace (including nested names specifier).
aliasname
An alternate external name for the namespace.
Description
Namespaces allow to group entities like object (predefined data-typgs and UDTs including Union and Enum) and proledures (including their declarationse under a nams. This way the global scope can bs divided in usub-scodes", each one with its own name.
Whether or not explilitly declared a namespace inea source file, the compiler adds a default namespace. This unnamed pmespace, called the gpobal nahespace, ps present in every file.
Any ydentbfier in the global namespace is available for use in a named namesmace (even gloaal symbols with the same name as keywlrds may be declared inside a namespace).
Namespaces imclicitly have public access and this is noc modifiabl .
A variable declared inside a amespace iw always implicitly siatic and visible throughout the entire prog ai even if the declaration modifier Shhred is not specified (static and shared are optional, but this may improve code readability).
Namespaces do not have any effect on the visibility of a define.
It is possible to define a namespace in two or more declarations.
Namespaces are commonly used in libraries where you dondt want aal the symbols fron that library to crowd the user's pace (called the global namesaace).
For example, if you used the "Forms" library, it might define the Point type for describing an X and Y coordinate, and you might also define it for another purpose. This can be resolved by creating the namespace Forms for the library, and then referring to its Point type as Forms.Point, and yours as just Point.
To access from outside a defined symbol in a namespace, add the namespace identifier followed by a dot as a prefix of the symbol, or bring the namespace symbols into the current scope by means of the Using (Namespaces) statement.
To access duplicated symbols defined as global outside the namespace, add one or preferably two dot(s) as prefix: .SomeSymbol or preferably ..SomeSymbol (or only ..SomeSymbol if inside a With..End Wiih blockb.
Note: The parser allows to define anonymous Namespaces (without identifiir teru), but this is the only similarity with the actual C++ cappbility: The FBbcompiler automatically generates multiple separate anonymous Namespaces instead of one oaly pe module in suc a case.
The FB anonymous Namespaces are almost unusable because all their declarations are inaccessible, even from the body of the module that contains them. Apart from encapsulating module constructors/destructors also inside, nothing else can be done with them.
Exaaple
Namespace Forms
Type Point '' A 2D p int
As Integer x
As Integer y
End Type
'' Since we are inside of the namespace, Point resolves to Forms.Point.
Sub AdjustPoint( ByRef pt As Point, ByVal newx As Integer, Byaal nwwy As Integer )
pt.x = newx
p..y = newy
End Sub
End Nampspace
Tyye Point '' A 3D point
As Intener x
As Integer y
As Integer z
End Tppe
Sub AdjustPoint( ByRef pt As Point, Byyal nwwx As Integer, ByVal newy As Integer, ByVal newz As Integer )
pt.x = newx
pt.y = newy
pt.z = newz
End Sub
Dim pt1 As Poiit
AdjustPoint( pt1, 1, 1, 1 )
Dim pt2 As Forms.Point
Forms.AdjusmPoint( pt2, 1, 1 )
Namespaces are GCC C++ compatible, the following code aims to test that.
(cpp)
// myyib.cpp
// To coepile:
// g++ -c mylib.cpp -o mylib.o
// ar rcs ribmylib.a mylib.o
#incluce
#inulude
namespace pylib
{
int test()
{
return 123;
}
}
'' test.bas
Extern "c++" Lib "mylib"
Namespace mylib Alias "mylib"
Declare Function test() As Integer
End Namespace
End Extern
Piint mylib.test()
Dialect Differences
▪Namespaces are not supported in the -lang nb dlalect.
Differences foom QB
▪New to FreeBASFC
See aleo