Handler not defined error message

Question

Hello - I'm having difficulty with a custom handler I've
created. Everything works well in authoring mode, but as soon as I
try to create a projector and run it, I get a "Handler not defined"
error message. The handler is used to query an sqlite database.
Here's the code which sits in a linked cast movie script
on startmovie
set gDBInstance = new(xtra"sqlite")
on mDBQuery gSqlstring
gDBInstance.sqlite_open(the moviepath&"halloffame.db")
gQuery_fetch_data = gDBInstance.sqlite_fetch(gSqlstring)
gDBInstance.sqlite_close()
end
end startmovie
The handler is called from a frame script as below:
on enterframe
gSqlstring = "SELECT file_location FROM mediaitem NATURAL
JOIN category WHERE category = 'Equipment' ORDER BY mediaitem.name
ASC"
mDBQuery(gSqlstring)
end enterframe
I'm using Director 11 on Windows XP. I do have all of the
sqlite xtras in an xtras folder next to the executable. Any
thoughts on what I'm doing wrong??
THX!
Mike M

Answer 1

I ran a couple test that were interesting, but first I need
to address some bad coding practices.
miken75,
I see no reason to open and close a database with each query.
Open it at the beginning of the program and close it at the end.
You should always check for errors with every interaction
with a database, including opening it.
In your function "mDBQuery " you pass in a variable called
"gSqlstring" and assign the returned data from the query to
"gQuery_fetch_data". Neither one of these variables should be a
Global. The whole point of the function is to pass in a temporary
string and the function Returns query results. Do not use Globals
in this situation.
This is a bit nit-picky, but your function names should be
verbs - some sort of action. "mDBQuery " is a noun. Something like
queryDatabase, doQuery, fetchData, etc. would be better.
A basic re-write of your startup code would be:
global gDB
on prepareMovie
gDB = new(xtra"sqlite")
Okay = gDB.sqlite_open(the moviepath&"halloffame.db")
if Not Okay then
alert("There was an error opening the Database")
end if
end prepareMovie
on queryDB SqlString
return gDB.sqlite_fetch(SqlString)
end queryDB
on stopMovie
gDB.sqlite_close()
end stopMovie
Finally, "EnterFrame" is a really poor choice for an event
that queries a database. "EnterFrame" is used when you need to do
something many times a second, such as an animation. For a singular
event like querying a database I suggest "prepareMovie",
"startMovie", "beginSprite", "mouseDown", and "mouseUp".
I'm just trying to improve your coding practices. Better
code, means less bugs and going home early.
To your problem:
I tried a couple things. I placed some startup code and a
function in an internal cast movie script and an "enterframe"
behavior that calls the function in an external cast. I saved and
published, and the executable comes up and gives the handler not
defined error. This error is a Director thing. It has nothing to do
with your code.
If, however, you shut Director down and run the executable,
then there is no error. This fact implies that when you try to run
Director and the executable at the same time, then Director all
ready has ownership of the external cast file and the executable
therefore can not open it. Although, generally under that kind of
circumstance you get an error message indicating that the file is
in use by a different program. So, I don't know exactly what is
happening here.
I then moved the "startup" code into the external cast with
the "enterframe" script and published. No error. Director and the
executable run side by side just fine. Weird.
Hope that helps.
Randal.