Determine if a text frame exists

[step]

Is it possible to determine whether a text frame of a certain name exists?

I'm populating (via OnRecordStart) a series of text frames with variable information and if the text frame doesn't exist for a version, I don't want FP to attempt to assign content to it. I realize that this won't be an issue during composition but I'm mainly asking in order to not get errors at validation.

Here's what I'm trying to do:

(FindTextFrame("Rate1_" + Field("version")).exists) ? FindTextFrame("Rate1_" + Field("version")).content = Field("rate1") : "";
(FindTextFrame("Rate2_" + Field("version")).exists) ? FindTextFrame("Rate2_" + Field("version")).content = Field("rate2") : "";

[scubajbc]

You should be able to use...

try
{
whatever code
}

catch (e)
{
if whatever code errors, run this code
}

[ThomasLewis]

Sorry to pull up such an old post but I was unable to find anything similar. I'm running into the same issue where I need to check if a frame exists in validation.

Using the Try/Catch method still causes the validator to return "null". Is there any way around that?

[Dan Korn]

Originally Posted by ThomasLewis

Sorry to pull up such an old post but I was unable to find anything similar. I'm running into the same issue where I need to check if a frame exists in validation.

Using the Try/Catch method still causes the validator to return "null". Is there any way around that?

I don't know what you mean. I'm not very good at guessing what's in your rule without seeing it.

A try/catch statement doesn't make a rule return anything, unless there's a return statement inside the catch block.

Also, you should be calling FindTextFrame inside of the OnRecordStart callback rule, which doesn't need to return anything anyway.

So... I'm not sure what the problem is in some code that I can't see.

[Dan Korn]

Maybe this will help. Here's how I would answer the original question. Again, these examples would all be in the OnRecordStart rule.

try
{
    FindTextFrame("Rate1_" + Field("version")).content = Field("rate1");
}
catch (e)
{
}

try
{
    FindTextFrame("Rate2_" + Field("version")).content = Field("rate2");
}
catch (e)
{
}

Or, more generally:

var myFrame;
try
{
    myFrame = FindTextFrame("your frame name");
}
catch (e)
{
    Print('Text frame not found!'); // <- or skip this if you want
}
if (myFrame)
{
    myFrame.content = "Hello there!"; // <- or whatever else you need to do
}

You could even make a function:

function TryToFindTextFrame(name)
{
    try
    {
        return FindTextFrame(name);
    }
    catch (e)
    {
        Print('Text frame "' + name + '" not found!'); // <- or skip this if you want
        return null;
    }
}

And call it like so:

var myFrame = TryToFindTextFrame("your frame name");
if (myFrame)
    myFrame.content = "Hello there!";

Or you could make a function to do whatever you need:

function SetTextFrameContent(frameName, content)
{
    try
    {
        FindTextFrame(frameName).content = content;
    }
    catch (e)
    {
        Print('Text frame "' + frameName+ '" not found!'); // <- or skip this if you want
    }
}

And simply call that:

SetTextFrameContent("your frame name", "Hello there!");

Or, back to the original question:

SetTextFrameContent("Rate1_" + Field("version"), Field("rate1"));
SetTextFrameContent("Rate2_" + Field("version"), Field("rate2"));

[ThomasLewis]

Those examples were all very helpful.

I'll try to explain where the issue is. I have a series of templates that all use very similar javascript for the OnRecordStart callback but also require the operator to modify the text frames on a per job basis.

Instead of maintaining all the code in each template I am using the Load function to bring in a single JS file. These templates will be used by operators that would be unable to diagnose javascript issues but can understand errors returned by validation.

The thought was to have them simply open OnRecordStart and tap the validate button. If everything checks out, great. But if one of the text frames is missing, then it would return an error specified in the script.

This is where my confusion came in. If you put return "test" directly into OnRecordStart, it will actually return "test" to the user. However, if you put return "test", or anything else, into an externally loaded JS file, it returns "null".

I was attempting the try/catch method and instead of nothing happening, I wanted to use return to return an actual "hey, you forgot to put in the text frame", instead it returns "null".

So, the examples all work fine, I guess the real issue is I am unable to return a custom message when text frame is not found.

[Dan Korn]

Originally Posted by ThomasLewis

Instead of maintaining all the code in each template I am using the Load function to bring in a single JS file. These templates will be used by operators that would be unable to diagnose javascript issues but can understand errors returned by validation.

Okay. The explanation is somewhat helpful. But still, I don't have any of your files, so I can only look at this through a very narrow keyhole.

Originally Posted by ThomasLewis

The thought was to have them simply open OnRecordStart and tap the validate button. If everything checks out, great. But if one of the text frames is missing, then it would return an error specified in the script.

This is where my confusion came in. If you put return "test" directly into OnRecordStart, it will actually return "test" to the user. However, if you put return "test", or anything else, into an externally loaded JS file, it returns "null".

That's not true. At least that's not true in my experience. I've written plenty of external JS files, and put returns in them, and had the return value show up when I validate a rule that's loading an external JS file and calling functions in it.

I suspect that you're putting the "return" in the wrong place. The thing about an external JS file is that it doesn't "return" anything. Your external JS file can have one or more functions in it, and your rules can call those functions, and each function can return something, but that's not the same as just putting a "return" statement in the JS file, outside of any function.

Again, though, instead of having to guess at what's in your JS file, it would be easier to for me diagnose it if I could look at it.

Furthermore, if there's really an error that you want the template designer to see, then instead of simply returning a message, you probably want to throw it instead, so that it'generates an exception. This has a couple of advantages over simply a return value: First, the box that pops up when you click Validate will have an error icon with it, which denotes an error condition much more explicitly than just the default message box with the title "Expressions OK". Second, the error message pops up when you try to save the rule, even if you don't click Validate. More about how to throw an exception instead of just returning a message below....

Also, putting on my moderator hat, it seems that your question is not really about determining whether a frame exists (the original question in this thread). Your question is really about how to return an error from an external JS file to the Rule Editor at validation time. So it really should be a new thread for this new question. And even if we figure it out the answer to your question here, that answer will only serve to confuse anyone who finds this thread later and just wants to know the answer to the original question, especially since it's highly unlikely that they'll be using an external JS file.

Originally Posted by ThomasLewis

I was attempting the try/catch method and instead of nothing happening, I wanted to use return to return an actual "hey, you forgot to put in the text frame", instead it returns "null".

Again, I think that's because you're returning something in the wrong place, but I can't really know for sure without seeing your code.

Originally Posted by ThomasLewis

So, the examples all work fine, I guess the real issue is I am unable to return a custom message when text frame is not found.

"... from an external JS file," is really the end of that statement. The code I provided in my previous post does answer the original question.

So, let's try to answer your question about returning an error from an external JS file.

First of all, what's wrong with the exception message that gets thrown by default when the a frame with the name passed to FindTextFrame isn't found? You know, "Error in FindFrame, no frame named 'Rate1_whatever'"?

Anyway, since you don't like that message, you can certainly throw whatever exception message you want, like so:

function TryToFindTextFrame(name)
{
    try
    {
        return FindTextFrame(name);
    }
    catch (e)
    {
        throw 'Hey, you forgot to put in the text frame named "' + name + '"!';
    }
}

You can even add to the default exception message if you want:

function TryToFindTextFrame(name)
{
    try
    {
        return FindTextFrame(name);
    }
    catch (e)
    {
        throw "Error calling external JS function: " + e;
    }
}

Or you can throw an exception for any condition you want, such as if some kind of business logic is not met, or a field value doesn't conform to some kind of pattern, or basically anything. It doesn't even have to be in an existing "catch" block; you can just throw whenever; for instance:

if (!Field("version"))
    throw "Invalid data!";

Learning how to throw and handle exceptions effectively is an important part of writing code, especially code that other people will be using. Professional programmers often talk about a variation of the "80/20 rule," which says that you'll spend 20 percent of the time writing the code for any program to handle cases where all of the inputs are in the correct and expected formats, and 80 percent of the time writing code to try to gracefully handle invalid data and other error conditions and report meaningful error messages back to the user of your code, or the end user of the program.

[ThomasLewis]

Attached is my template with the external JS file. When you open OnRecordStart and click validate, it returns "null". If I paste the code from the JS file directly into OnRecordStart, it returns the error as you would expect.

I get where you are coming from trying to keep things organized. Hopefully this will make more sense with the attached sample.

[step]

Try putting your logic in a function (called "validateTextFrames" for example) and then call it from your OnRecordStart callback.

JavaScript file:

function validateTextFrames() {
  // Your required frames.
  var frames = [
    'Your First Text Frame Name',
    'Your Second Text Frame Name'
  ];

  for (var i in frames) {
    try {
      var frameName = frames[i];
      if (FindTextFrame(frameName))
        delete frames[i];
    } catch (e) {}
  }
  if ((frames = frames.filter(String)).length)
    ReportError('Missing required text frame(s):\n"' + frames.join('"\n"') + '"');
}

OnRecordStart callback:

Load("errortest.js");
validateTextFrames();

As far as returning a value from your external JS file, you have to return the function in your FP callback:
JS file:

function testReturn() {
  return 'hello from your external js file!';
}

OnRecordStart:

Load("errortest.js");
return testReturn();

[ThomasLewis]

Adding that extra function call directly to OnRecordStart did the trick. It's working perfectly now. It's just a matter of updating all the templates to include that extra line. Thanks so much for all the help