I have a perl mason component which is called to display an html page containing threaded comments. It uses Class DBI for loading from a MySQL database.
The problem is that sometimes, and I mean sometimes, very irregularly a variable loses its value partway through the code. I am not changing the code between when it starts and stops happening, just reloading the page. It's not even that it just has the value on one page load and not the next. It's that on one page load you can print something to show that the variable contains a ref to an object (a "Person" with a name, etc.) and later on in the code on that same page load you can print that again and show that it doesn't. On the next page load the variable may retain its value all the way through. The only thing that is happening is that the variable gets passed through a call to $m->comp(), and a default gets applied if it is empty.
Further, it happens for each and every comment, effectively losing its value many times in the same page load.
Unfortunately (or fortunately, depending on how you look at it) I can't post all the code involved verbatim, but it boils down to the following, note the two commented lines marked "HERE":
<%init>
my #comments = $dc->document->search("type = 'comment'");
</%init>
<div>
<& '.comments', all_comments => \#comments &>
</div>
<%def .comments>
<%args>
$all_comments
</%args>
<%init>
my #comments;
#comments = #$all_comments;
</%init>
% for my $c (#comments) {
% my $poster = p($c->get_value('poster'));
% $poster = Person->get_anonymous unless ref $poster;
% # HERE: The variable is a ref to a given Person.
% $m->comp('.comment', poster => $poster);
% }
</%def>
<%def .comment>
<%args>
$poster => Person->get_anonymous
</%args>
<%init>
# HERE: The variable is now the result of Person->get_anonymous instead.
unless (ref $poster) {
$poster = Person->get_anonymous;
}
</%init>
<p><% $poster->id == 1 ? ' (anonymous)' : $poster->fullname %></p>
</%def>
I've tried removing that default, in which case I get an empty variable.
This is a years old problem scrutinized down to these few lines of code where, programmatically speaking, something impossible seems to be happening. I'm left with a possible bug in Mason, or maybe some combination of things like some voodoo between Class DBI and the database losing a connection, or something I don't know about $m->comp().
The only other clue I have is that when I've added something to the page, I've had the problem show up to an entirely new variable. Unfortunately, I never know when the problem is going to happen, and it happens seldom enough that I won't be able to go throw some suggested debugging code into it that will immediately give me something to report back. I'm only hoping for the off chance that somebody has experienced something similar or knows some possible problem that might explain what is going on.
Related
So I have created a huge screen that essentially just shows the robot status for every robot in this factory (individually)… At the very end of the project, they decided they want one object on the screen that blinks if any of the 300 robots fault. I am trying to think of a way to make this work. Maybe a global script of some kind? Problem is, I do not do much scripting in Cimplicity, so any help is appreciated.
All the points that are currently used on this screen (to indicate a fault) have very similar names… as in, the beginning is the same… so I was thinking of a script that could maybe recognize if a bit is high based on PART of it's string name characteristic. The end will change a little each time, but I am sure there is a way to only look for part of a string and negate the rest. If the end has to be hard coded, that's fine.
You can use a Python script in Cimplicity.
I will not go into detail on the use of python in Cimplicity, which is well described in the documentation indicated above.
Here's an example of what can be done... note that I don't have a way to test it and, of course, this will work if the name of your robots in the declaration follows the format Robot_1, Robot_2, Robot_3 ... Robot_10 ... Robot_300 and it also depends on the Name and the Type of the fault variable... as you didn't define it, I imagine it can be an integer, with ZERO indicating no error. But if you use something other than that, you can easily change it.
import cimplicity
(...)
OneRobotWithFault = False
# Here you get the values and check for fault
for i in range(0, 300):
pointName = f'MyFactory.Robot_{i}.FaultCode'
robotFaultCode = cimplicity.point_get(pointName)
if robotFaultCode > 0:
OneRobotWithFault = True
break
# Set the status to the variable "WeHaveRobotWithFault"
cimplicity.point_set("WeHaveRobotWithFault", OneRobotWithFault)
Ok, I've been stuggling with this one for a while, and have spent a lot of time trying different things to do something that I have done very easily using PHP.
I am trying to iterate over a list while keeping track of a variable locally, while spitting out HTML attempting to populate a table.
Attempt #1:
#{
var curDate : Date = null
for(ind <- indicators){
if(curDate == null || !curDate.equals(ind.getFirstFound())){
curDate = ind.getFirstFound()
<tr><th colspan='5' class='day'>#(ind.getFirstFound())</th></tr>
<tr><th>Document ID</th><th>Value</th><th>Owner</th><th>Document Title / Comment</th></tr>
}
}
}
I attempt too user a scala block statement to allow me to keep curDate as a variable within the created scope. This block correctly maintains curDate state, but does not allow me to output anything to the DOM. I did not actually expect this to compile, due to my unescaped, randomly thrown in HTML, but it does. this loop simply places nothing on the DOM, although the decision structure is correctly executed on the server.
I tried escaping using #Html('...'), but that produced compile errors.
Attempt #2:
A lot of google searches led me to the "for comprehension":
#for(ind <- indicators; curDate = ind.getFirstFound()){
#if(curDate == null || !curDate.equals(ind.getFirstFound())){
#(curDate = ind.getFirstFound())
}
<tr><th colspan='5' class='day'>#(ind.getFirstFound())</th></tr>
<tr><th>Document ID</th><th>Value</th><th>Owner</th><th>Document Title / Comment</th></tr>
}
Without the if statement in this block, this is the closest I got to doing what I actually wanted, but apparently I am not allowed to reassign a non-reference type, which is why I was hoping attempt #1's reference declaration of curDate : Date = null would work. This attempt gets me the HTML on the page (again, if i remove the nested if statement) but doesn't get me the
My question is, how do i implement this intention? I am very painfully aware of my lack of Scala knowledge, which is being exacerbated by Play templating syntax. I am not sure what to do.
Thanks in advance!
Play's template language is very geared towards functional programming. It might be possible to achieve what you want to achieve using mutable state, but you'll probably be best going with the flow, and using a functional solution.
If you want to maintain state between iterations of a loop in functional programming, that can be done by doing a fold - you start with some state, and on each iteration, you get the previous state and the next element, and you then return the new state based on those two things.
So, looking at your first solution, it looks like what you're trying to do is only print an element out if it's date is different from the previous one, is that correct? Another way of putting this is you want to filter out all the elements that have a date that's the same date as the previous one. Expressing that in terms of a fold, we're going to fold the elements into a sequence (our initial state), and if the last element of the folded sequence has a different date to the current one, we add it, otherwise we ignore it.
Our fold looks like this:
indicators.foldLeft(Vector.empty[Indicator]) { (collected, next) =>
if (collected.lastOption.forall(_.getFirstFound != next.getFirstFound)) {
collected :+ next
} else {
collected
}
}
Just to explain the above, we're folding into a Vector because Vector has constant time append and last, List has n time. The forall will return true if there is no last element in collected, otherwise if there is, it will return true if the passed in lambda evaluates to true. And in Scala, == invokes .equals (after doing a null check), so you don't need to use .equals in Scala.
So, putting this in a template:
#for(ind <- indicators.foldLeft(Vector.empty[Indicator]) { (collected, next) =>
if (collected.lastOption.forall(_.getFirstFound != next.getFirstFound)) {
collected :+ next
} else {
collected
}
}){
...
}
When fields are nested, there is a problem.
foreach (Word.Field field in this.Application.ActiveDocument.Fields)
{
field.Update();
text = field.Result.Text;
}
The above code does not work.
The process starts, but winds up in an endless loop or some other process that hangs the system.
Thinking about it, I can surmise that when you update a field, it might have an effect on the fields collection - thus, the loop fails.
Does anyone have any ideas on implementing this?
P.S. I know there is a Document.UpdateFields() method to update ALL fields. However, there are reasons why I cannot use this and need to only update specific field types.
My apologies! I was going to give an example of a nested field but was trying to test some more before sending anyone (Jack) on a goose-chase.
I waited and waited and waited, and after a good 2 or 3 minutes, it finished. After the last field, it crashed with this message:
Object has been deleted.
The error was generated from the following line inside the loop:
string text = field.Code.Text;
The template is being tested on mergefields that are not being found because I am testing without database connectivity. It would be odd, but explainable, that it goes through all the fields and then, at the end of the day, the very OUTER IF field's result is "Error! Reference source not found." But I still don't get why this could happen.
Nor do I understand why looping takes 3 minutes while a call to document.Fields.Update() will do the same thing in about 1 second and NOT result in the error described above.
Again, my apologies. I never considered updating inside a loop would be vastly slower that a call to doc.fields.update().
I've been messing around with CGI::application the past couple of days and decided to create a really basic forum: the first page displays all posts (only first level, no replies or anything) and a form which can be used to create a new post.
The issue I'm running into is that the data that gets entered into the form never gets inserted into the SQLite database.
Here's the sub procedure I'm having trouble with:
sub newpost {
my $self = shift;
if ( $self->param() ){
my $dbh = DBI->connect("dbi:SQLite:dbname=$database_file","","");
my $sth = $dbh->prepare("INSERT INTO posts (author, time, text) VALUES('testuser', '2011-10-23', 'This is a test!')");
$sth->execute();
$self->header_type('redirect');
$self->header_props(-url=> '?rm=viewall');
}
else {
my $tmpl_obj = $self->load_tmpl('newpost.html');
return $tmpl_obj->output();
}
What happens correctly is that when the newpost run mode is first called, the code within the else statement is run (the template with the form is loaded). The action for the form calls this same run mode, but now that parameters are being provided, the code in the if statement is run. I've checked the SQL code itself and it works, so there must be something else I'm over looking.
Also, is it considered best practice to go about implementing the form logic in this way?
Thanks
You're confusing $self->param() with $self->query->param. The 1st is per-request application level parameters (stuff you might set in one method and use again in another method) and the 2nd are the parameters from the GET query string or the POST body of the request. If you're expecting something from the user it will be in $self->query->param.
BTW, the $self->query object is a normal CGI object, so see it's documentation for specifics.
I'm in a web scripting class, and honestly and unfortunately, it has come second to my networking and design and analysis classes. Because of this I find I encounter problems that may be mundane but can't find the solution to it easily.
I am writing a CGI form that is supposed to work with a MySQL DB. I can insert and delete into the DB just fine. My problem comes when querying the DB.
My code compiles fine and I don't get errors when trying to "display" the info in the DB through the browser but the data and text doesn't in fact display. The code in question is here:
print br, 'test';
my $dbh = DBI->connect("DBI:mysql:austinc4", "*******", "*******", {RaiseError => 1} );
my $usersstatement = "select * from users";
my $projstatment = "select * from projects";
# Get the handle
my $userinfo = $dbh->query($usersstatement);
my $projinfo = $dbh->query($projstatement);
# Fetch rows
while (#userrow = $userinfo->fetchrow()) {
print $userrow[0], br;
}
print 'end';
This code is in an if statement that is surrounded by the print header, start_html, form, /form, end_html. I was just trying to debug and find out what was happening and printed the statements test and end. It prints out test but doesn't print out end. It also doesn't print out the data in my DB, which happens to come before I print out end.
What I believe I am doing is:
Connecting to my DB
Forming a string the contains the command/request to the DB
Getting a handle for my query I perform on the DB
Fetching a row from my handle
Printing the first field in the row I fetched from my table
But I don't see why my data wouldn't print out as well as the end text. I looked in DB and it does in fact contain data in the DB and the table that I am trying to get data from.
This one has got me stumped, so I appreciate any help. Thanks again. =)
Solution:
I was using a that wasn't supported by the modules I was including. This leads me to another question. How can I detect errors like this? My program does in fact compile correctly and the webpage doesn't "break". Aside from me double checking that all the methods I do use are valid, do I just see something like text not being displayed and assume that an error like this occurred?
Upon reading the comments, the reason your program is broken is because query() does not execute an SQL query. Therefore you are probably calling an undefined subroutine unless this is a wrapper you have defined elsewhere.
Here is my original posting of helpful hints, which still apply:
I hope you have use CGI, use DBI, etc... and use CGI::Carp and use strict;
Look in /var/log/apache2/access.log or error.log for the bugs
Realize that the first thing a CGI script prints MUST be a valid header or the web server and browser become unhappy and often nothing else displays.
Because of #3 print the header first BEFORE you do anything, especially before you connect to the database where the script may die or print something else because otherwise the errors or other messages will be emitted before the header.
If you still don't see an error go back to #2.
CGIs that use CGI.pm can be run from a command line in a terminal session without going through the webserver. This is also a good way to debug.