[Mapserver-users] Re: Implementing querying functionality usingPerl MapScript
Lowell Filak
lfilak at medinaco.org
Tue Jul 15 16:21:05 EDT 2003
Eric!
Thanks for pointing out my error (whether you intended to or not).
I forgot $hDBF->get_record($rec_no) pulls the record by number as
opposed to complicating things with a loop as I previously suggested.
Lowell
The following message was sent by Eric Bridger <eric at gomoos.org> on 15
Jul 2003 11:30:06 +0000.
> You can find XBase here:
> http://search.cpan.org/author/JANPAZ/DBD-XBase-0.234/lib/XBase.pm
> You will need to install it. The mapserver install does not do this for
> you.
>
> The version shouldn't matter. As explained below, Mapserver's query
> results will give you the index into the dbf file.
>
> I think I recall some users having problems using the DBF functions in
> Perl/Mapscript. I too, always use XBase. E.g.
>
> my $datafile = $layerObj->{data};
> # To get the attributes open the dbf file.
>
> my $dbfile = $datafile . '.dbf';
> my $hDBF = new XBase "$dbfile" or die XBase->errstr;
> my @row = $hDBF->get_record($rec_no) or warn $hDBF->errstr . "\n";
>
> Eric
>
>
> On Tue, 2003-07-15 at 14:09, pkishor_98 wrote:
> > --- In mapserver-users at yahoogroups.com, AMC Story <s9646183 at s...> wrote:
> > > Thanks, I'll try to be a bit more specific this time :)
> >
> > good. often we get vague-ish questions, and it is almost impossible
for anyone to
> > answer them. it seems obvious on hindsight, but most of us are
likely working in
> > environments different from that of the person asking the question
-- it is simply a
> > waste of bandwidth and energy trying to "imagine" what the problem
might be.
> > anyway, ;-)
> >
> >
> > >
> > > Basically, I'd like to be able to select a point object from the
map, and then
> > > display a new pop-up box, which would give the user all the
information about
> > > that point feature which is stored in the dbf file, and perhaps
also include a
> > > map in this pop up window which would highlight the selected
feature in a
> > > different colour or with a different symbol. Not quite sure how
to do the pop-
> > > up box thing yet, but I seem to remember some tips on this in the
archive, so
> > > I'll look at that once I've figured out how to do the basics.
> >
> > pop-up is a javascript or basic html question. Use js to create a
new window, or use
> > "target=_blank" on a link to open a new window.
> >
> > for a map being displayed in the pop-up, see the itasca demo. It
does it very well.
> >
> > first concentrate on getting it all to work in a regular html
window. Once it works
> > there, you can always convert it into a pop-up or a frames-based app.
> >
> > >
> > > So far, I've got to the point where I can display the shapeindex
of the
> > > selected point,
> > >
> > > ie. $rec_no = $result_feature->{shapeindex};
> > >
> > > but I'm now struggling to work out how to access the attributes of
the feature
> > > in the dbf file with that record number. In some of the examples,
the XBase
> > > module is used. I don't seem to be able to access this (and I've
tried xdb and
> > > Xbase too) but I could possibly get it installed if it's necessary.
> >
> > I have used Xbase like so
> >
> > ##############################
> > my $table = new Xbase;
> >
> > $table->open_dbf($shapefile . '.dbf') or die Xbase->errstr;
> > ##############################
> >
> > but there are more detailed examples available. Just read the docs
for Xbase.
> >
> > In concept, you will use the shapeindex to grab the specific record.
The shapeindex
> > indicates the row in the dbf table. Keep in mind, the first row in
the dbf table is the
> > header row... the names of the columns. The second row corresponds
to the first
> > shapeindex, etc.
> >
> > >
> > > I was wondering though whether I could use methods of the DBFInfo
class or some
> > > of the miscellaneous functions such as msDBFReadStringAttribute
which I saw
> > > listed on the Perl MapScript Reference some time ago, but which
now seem to
> > > have disappeared. Are these still supported, and is there any
documentation
> > > somewhere for them?
> >
> > Yes, you can use the DBF functions in Perl/Mapscript. I haven't... I
just use the Xbase
> > module. Make sure you have the latest version, and read the docs.
You can also use
> > XBase... the syntax is slightly different.
> >
> > >
> > >
> > > Quoting pkishor_98 <pkishor at g...>:
> > >
> > > > --- In mapserver-users at yahoogroups.com, AMC Story <s9646183 at s...>
> > > > wrote:
> > > > > Hi there everyone,
> > > > >
> > > > > I've been using Perl MapScript to develop the interface
> > > > > of my application, and am now wanting to implement the
> > > > > querying functionality that I had going with
> > > > > the old mapserver CGI version, but now with MapScript.
> > > >
> > > > could you elaborate more on --
> > > >
> > > > - what have you already developed with Perl/Mapscript; and
> > > > - what you mean by "querying functionality"
> > > >
> > > > Until you do that, I am going to assume you mean identifying a
feature
> > > > based on the user's mouse-click.
> > > >
> > > > > I was wondering if there are any examples of the code
> > > > > needed to do this, as I can't seem to find
> > > > > anything more than very brief (and apparently incorrect!)
> > > > > snippets in the
> > > > > archives.
> > > >
> > > > which archives did you look at? There are several very nice examples
> > > > on the wiki, and in the Perl/Mapscript docs. The best, most complete
> > > > example is the mapquakes.pl script. It shows you the building
blocks.
> > > >
> > > > Briefly... you capture the mouse clicks and use them to create
the new
> > > > map envelope and generate a new image. If you are querying...
you once
> > > > again use the mouse clicks to get the shapeindex and then get its
> > > > associated attribute data from either the <shape>.dbf or a related
> > > > external database table. Keep in mind, the mouse clicks would be
> > > > imagespace, and will have to be converted to geographic space before
> > > > doing anything with them.
> > > >
> > > > There are definitely fewer ready-to-use, code capsules for
> > > > Perl/Mapscript, and some of us have talked about remedying the
> > > > situation. Most Perl/Mapscript users, however, have found the
existing
> > > > examples quite helpful in guiding them and setting them on the
correct
> > > > path to developing their own code. Each application is
different, and
> > > > it is hard to provide a demo that will work for everyone.
> > > >
> > > > Please look at the above mentioned examples on the wiki, and then if
> > > > you have specific questions come and ask us. One of us will be
able to
> > > > help you.
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Mapserver-users mailing list
> > > > Mapserver-users at l...
> > > > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> > > >
> > > _______________________________________________
> > > Mapserver-users mailing list
> > > Mapserver-users at l...
> > > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> >
> > _______________________________________________
> > Mapserver-users mailing list
> > Mapserver-users at lists.gis.umn.edu
> > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> >
>
> _______________________________________________
> Mapserver-users mailing list
> Mapserver-users at lists.gis.umn.edu
> http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
More information about the mapserver-users
mailing list