View source for Gambas

[[Computing]]: [[Software]]: [[Gambas]]{{seedling}}
[[Gambas]] is a programming language and [[IDE (programming)|IDE]].
==Overview==
* intended to fill the same niche as [[VB]], though not intended to be code-compatible
* currently only available for [[Linux]] and other Unix-derivatives (there is a partially-functioning Windows version)
* [[open-source]]
==Articles==
* [[Gambas Reference]]
==Reference==
* [http://gambas.sourceforge.net/ Gambas homepage]
** [http://gambasdoc.org/help Gambas wiki] is apparently written ''in'' Gambas, but lacks a search function (and many other common [[wiki]] functions), and requires an account in order to edit, which in turn requires an email to the author.
* [[Wikipedia:Gambas|Wikipedia]]
* [[wikibooks:Gambas|Wikibooks]]
* [http://www.laclavedefa.org/codigo_abierto/gambas_tutorial/ tutorials] (English, Spanish)
* [http://www.linuxbasic.net/ Linux Basic] forum: ostensibly for "the new breed of Basics coming out for the Linux operating system", but the focus seems to be mostly (or entirely) on Gambas
===resources===
* [irc://irc.freenode.net/#gambas Gambas] IRC channel

==Stumbling Blocks==
===Unanswered===
* '''Q''': How do you access [[kioslave]]s in code?
* '''Q''': Is it possible to do [[continuous forms]] as in [[MS Access]]? It seems likely that it can be done with some coding...
* '''Q''': Is there any equivalent to the line-continuation syntax (space + underscore) in VB?
* '''Q''': Is there a general language syntax tutorial or reference anywhere?

===Solved===
* One of the more confusing aspects of Gambas (for a Visual Basic user, anyway) is that Gambas's events do not pass parameters; instead, you have to know where to fetch them from:
** '''Form resize''': the size is easily available as a form property ("ME.")
** '''Mouse clicks''': use the [[Mouse object (Gambas)|Mouse object]]
** '''Key presses''': use the [[Key object (Gambas)|Key object]]
** '''Controls in a group''': use the [[LAST (Gambas)|LAST]] keyword
*** The most obvious solution would have been for the event to pass the control as a parameter; Gambas events don't seem to use parameters. Another intuitive solution would have been for the group itself to appear on the form's list of controls/methods, as an alias for the currently active/effective control. Finally, if the form had an ActiveControl property, I could pull the .Tag value from there, although I would expect to run into problems using this technique under some circumstances. '''Answer''': The LAST keyword refers to the control which generated the current event.
* Another minor thing to remember is that calls to Gambas subroutines always put parentheses around the parameter list (VB subroutines do not, unless the subroutine is a function or property and the return value is being retrieved).
* '''Q''': How do you open a file-browsing dialog that uses KDE's [[kioslave]] feature? ([http://gambasdoc.org/help/comp/gb.form/dirchooser DirChooser] in gb.form lets you choose a local folder only.)
** '''A''': [http://gambasdoc.org/help/comp/gb.qt.kde/dialog/selectdirectory Dialog.SelectDirectory] in [http://gambasdoc.org/help/comp/gb.qt.kde gb.qt.kde] provides this.
* An "invalid assignment" error can be caused by an undeclared variable, e.g. "A = B" if A has not been declared.
* Properties cannot accept additional arguments (other than the value being processed or retrieved). Workaround: instead of '''property Value''', have '''function GetValue''' and '''sub PutValue(iVal)'''. Not elegant, but functionally equivalent. Another option may be to have the passed data be a hash, but that is probably only efficient in certain rare circumstances; otherwise it involves extra coding to put the data in the hash and get it back out again.
* This may be a '''compiler bug''' or at least an undocumented feature: a class with no member variables seems to be automatically classified as "[[static class (Gambas)|static]]", and therefore cannot be used with the NEW operator. To get around the problem, declare a dummy member variable (e.g. "private strDummy as string").

==Flaws==
* (Major) Apparently there is no way to instantiate [[virtual classes within Gambas]]; a descendant class must be written using C++. This means that you cannot effectively use any component (or other class), such as ListView, which returns data using virtual classes, without writing C++ code.
* (Major, may be a problem for debugging) No "view stack" window
* (Major but livable) Hovering over variables at runtime does not display their current value, as in VB
* (Major but livable) Help is not context-sensitive
* (Major but livable) There is no equivalent to the VB right-click "Go to definition" menu command
* (Annoying; bad for writing good code) Constants cannot be defined using other constants (e.g. A = "something" & B, where A and B are both constants)
* (Minor) SHIFT-TAB does not unindent
* (Minor) Although the syntax for accessing field data is nominally similar to VB's syntax, a variant which works under VB does not work in Gambas:
{|
|-
| valign=top |
<center>'''works in VB'''</center>
 '''with''' objData
    intID = !ID
    strName = !Name
 '''end with'''
| valign=top |
<center>'''required form in Gambas'''</center>
 intID = objData!ID
 strName = objData!Name
|}
* (Minor) Identifiers are not automatically capitalized to match their declaration, as in VB; fortunately, identifiers are not case-sensitive for compilation, so this doesn't make things ugly the way it does in C/C++. (The pop-up list of methods/properties/events ''sometimes'' won't show up, however, unless the object's name is properly capitalized.)
* The field-list popup isn't smart in certain circumstances:
*# Type me.controlname.field (use a real control name and a real field name)
*# Move cursor somewhere else
*# go back to same line, and highlight the "." between "controlname" and "field"
*# type "."
*#* (minor) The list doesn't automatically select the field which was there already
*#* (annoying) When you select the field you want, it is inserted between "." and the fieldname that was there before. This follows logically from the editing rules, but is not what we want to happen; the selected fieldname should replace the old fieldname.

==Notes==
* The Help system appears to be wiki-based, possibly feeding directly off the Gambas wiki -- so any errors found can be corrected by anyone, in theory. Not sure how easy this is in practice. (Edit buttons do not appear in the Help app, so you would have to find the correct page on the wiki.)