Extends Wstringtype

Specifies a type which inherits a Wstring behavior

Syntax

Type|Union typename Extends Wstring [, base_typename]

...

End Type|Union

Description

Extends Wstring declares typename to inherit properties and behaviors of a WString. Purpose is to allow users to create custom string types (with i.e. dynamic memory management) that can integrate well in to existing fbc compiler built ins (good interoperability with fbc's WString type).

This declaration of such a UDT with a suitable Cast operator will instruct compiler to convert the UDT to a WString (in addition, other suitable operators as Let, [] (Pointer Index), Len, ..., can be also declared).

WString behaviour can be inherited directly, or indirectly and singly from a base-type.
WString behaviour can be inherited by a UDT also extending base_typename (a kind of pseudo multiple-inheritance).

By declaring a type (directly or indirectly) as Extends Wstring (in addition to defining a suitable Cast operator only), this promotes it fully WString type compatible, even with StrPtr/SAdd, LSet/RSet, and Select Case.

Remarks

Version

• Before fbc 1.09.0, this promotion was not yet fully WString type compatible with the built in functions Val/ValInt/ValLng/ValUInt/Valunlg and Left/Right.
  
• Since fbc 1.07.0
  
  

Dialect Differences

• Not available in the -lang qb dialect unless referenced with the alias __Extends __Wstring, but unusable because no member procedure is allowed in this dialect.
  
  

Differences from QB

• New to FreeBASIC
  
  

See also

• Type
  
• Union
  
• Extends
  
• WString
  
• Extends Zstring
  
  

Example

See Extends Zstring for similar examples.

Reference

• Documented in KeyPgExtendsWstring.html