Mailing List Archive: Re: IOS data

[REBOL] Re: IOS data

From: allenk:powerup:au at: 2-Oct-2001 23:19


----- Original Message -----
From: "Petr Krenzelok" <[Petr--Krenzelok--trz--cz]>
To: <[rebol-list--rebol--com]>
Sent: Tuesday, October 02, 2001 7:55 PM
Subject: [REBOL] Re: IOS data

> >
>
> Hi,
>
> > So I propose to start with a collection of descriptions for those
objects, so
> > that we all can base our work on these discriptions. It should even be
possible
> > to handle different versions of those objects, as Rebol supports checks
about
> > the presense of words in objects.
>
> How?
>
> value? obj/word ??? If word doesn't exist, it fails ... or -  in obj
'word?

Here is an example from a couple of apps that share data. Each of the apps
has slightly extended a msg obj. (Note: This is from express beta, and not
necessarily representative of the new IOS framework)

1. Presumably you know which features or fields in the data your app
supports. So you create a template object for the data, complete with
default values (in this case I set all to none).

msg-obj: context [fx: who: when: color: content: file: group: none]

2. the data is a simple block (which could be loaded from a file)
[who: "Allen" when:  2-Oct-2001/22:54:47+10:00 color: 200.100.50 file:
%msg0001.r group: "support" offset: 0x0 refresh: 1:00:00 content: "Test
Messgage"]

3. Make our object
if error? try [msg: make msg-obj load data][msg: make msg-obj []]

make object! [
    fx: none
    who: "Allen"
    when: 2-Oct-2001/22:54:47+10:00
    color: 200.100.50
    content: "Test Message"
    file: %msg0001.r
    group: "support"
    offset: 0x0
    refresh: 1:00
]

(Note how compact and extensible the REBOL block format is compared to XML
for transfering simple data.)

4. Now I can use the parameters of the object that my script knows about. I
can ignore the paremeters that I don't know about. And I can test for ones I
expect because of my defaults in the template.

if msg/fx [do really amazing fx stuff]
if msg/who [print ["Msg for " msg/who]

5. You can also find out if other words are present in the object,
>> found? in msg 'color
== true
>> found? in msg 'squid
== false

5. If I wanted to save this msg object I would use
save msg-file third msg

Cheers,

Allen K