[Gambas-user] Really basic basics

[Fabien Bodard]

2011/5/20 Rob <sourceforge-raindog2 at ...94...>:
> On Friday 20 May 2011 06:08, j h wrote:
>> For example a simple program
>>  has a window with a Valuebox, a button and a slider.   How do i program
>>  it so when i press the button the value of the slider is displayed in
>>  the valuebox? If anyone can carefull explain how, not just write the
>>  code, it would really help me get going! Thanks
>
> Fabien already posted the code, but as far as "how" goes:
>
> How you actually do it in the IDE:
>
> Double click the button, it'll create a Sub (subroutine) for you, and in
> that subroutine you write the one line of code that takes the value of the
> slider and puts it in the valuebox.  Press F5 and it'll compile and run
> your program.
>
> How it works:
>
> The button, slider and valuebox are all "objects".  This is how most
> languages work now: instead of just variables, the things you see on the
> screen are self-contained objects with their own code ("methods", though
> few languages actually use that term in the code) and variables of their
> own (most of which are called "properties").
>
> When the user clicks the button, an "event" is generated.  There was
> nothing like this in Sinclair BASIC and Amiga BASIC had only a little of
> that; the closest thing in 8- and 16-bit computing was the "interrupts"
> used in assembly language to jump to a particular section of code when the
> user pressed a key.  The OS gets the mouse button click, the windowing
> system determines the mouse is over your button, and sends the event to
> Gambas.  The Gambas interpreter checks to see if you have code to run when
> that event happens, and runs it for you, so all you have to think about is
> what happens next.
>
> In a 1980s BASIC program, you would have had a loop waiting for input to
> happen.  In Gambas, this is done by the interpreter (and much more
> efficiently), not your own code.  Event handlers you write, like
> Button1_Click in Fabien's example, replace the big lists of if/thens we
> used to write back then to figure out what the user did and take action
> based on it.
>
> Coming from totally procedural code on a single-tasking system like
> Sinclair BASIC, object-oriented programming with event handling can take a
> while to grasp.  VB, Javascript/AJAX, and most graphical programming in
> Java, C/C++, Python, etc. all work the same way nowadays, so once you
> figure it out in Gambas you'll probably be able to do it in any modern
> language you learn.
>
> Rob
>
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sorry i did it between two doors ='(
-- 
Fabien Bodard