Stefan Cameron on Forms
Building intelligent forms using Adobe LiveCycle Designer

'Instance Manager' Category Archive

Scripting Table Columns

A few days ago, Sergio, one of my regular commenters, posted a question about programmatically adding new columns to a table. My reply to his comment quickly turned into something that I thought should be promoted to a blog post so here it is.

This question required some investigation because it led me to the discovery of a bug related to adding/removing instances of a table column in a form viewed in a version of Acrobat prior to 8.0. More on that later in this post.

The short answer to Sergio’s question is that yes, in fact, you can modify the set of columns in a table programmatically at runtime. You can do this by either using the presence attribute — although this isn’t recommended because it can lead to data merging problems — or you can use Instance Managers to do it, which is the recommended method to use.

Here’s a sample form that contains a table with a “repeatable column”. Using the add and remove buttons that are provided, you can add and remove instances of the 3rd column.

Download Sample [pdf]

Minimum Requirements: Designer 7.1, Acrobat 7.0.5.

Table Structure

To better understand what’s going on here, I’ll start by explaining how tables are represented in XFA. In reality, there are no <table>, <tr> or <td> elements in XFA. What happens is that <subform layout=”table|row”> elements get used. When a subform represents a table, it’s layout attribute is set to table and when it represents a row, it’s set to row.

Table Subforms

If you read about using a subform’s Instance Manager in order to add/remove instances, you should know that a subform only becomes dynamic or repeatable once it’s placed in a flowed container and its set as repeatable using the Object palette’s Binding tab. By default, a <subform layout=”table”> element is flowed from top to bottom. Since the table subform contains row subforms which, in turn contain the cells, that means that every row in a table could easily be set as repeatable and then get an Instance Manager that you could use to add/remove instances of a particular row.

Row Subforms

Just like the table subform, a <subform layout=”row”> is flowed. Its flow direction, however, isn’t top to bottom, it’s right to left. This means that its contents — the cells — are flowed.

Cells and Columns

Table cells are little different. Essentially, since they reside in a row subform which is flowed from right to left, there’s no specific definition for what is a table cell. It’s simply any type of object (text, numeric field, subform, button, etc.) that’s placed within a row subform. The number of objects in the row determines the number of columns there are. Therefore, to have a 3×3 table, you would need 3 row subforms each containing 3 objects.

There’s no actual definition for a table column either. Table columns are inferred by the cells (put simply, without going into details about column spanning). This means that a column consists of objects in separate row subforms which are above and below each other (e.g. the first object on every row make-up the first column in a table).

Adding/Removing Columns

Given the explanations in my little “table primer” above, we now know that table cells are objects which are flowed from right to left within row subforms. Since row subforms are flowed by nature, it means that if a cell were a subform itself, it could be made repeatable and it would then get its own Instance Manager for free! And once we have Instance Managers, we can start adding and removing instances of those cells.

So the trick here lies in converting every cell which constitutes a column into a subform which then contains the type of object you would normally use to display information in that cell (e.g. a text field, a check box, etc.).

Now if you’ve never noticed the Type property on the Field tab in the Object palette before, you’ll want to check it out because it’s about to come in real handy for setting-up a dynamic table column which consists of cells which are all subforms. This property is used to change the type of the selected object(s). For instance, if you put a text field on a form and decide that it should have been a numeric field, you can change it’s type from text field to numeric field simply by using this property. Typically, you cannot change anything into a subform but when you select a table cell which is a text object (the default cell object type when you insert a new table into a form using the Insert Table menu command or the Table object in the Library’s Standard tab), you can, in fact, change it into a subform. So just select each cell in the column and change its type to a subform using this property. The result will be a cell which is a subform that contains a text object. Then you can change the text object into some other field type which better represents the data which will go into the cell.

Making Cell Subforms Repeatable

Unfortunately, this is one case where you’ll have to use the XML Source tab because the repeatable property isn’t available for cell subforms on the Object palette’s Binding tab. Since it’s a valid XFA setting, you can set this yourself using the XML Source.

Switch to the XML Source window by selecting “XML Source” from the top-level View menu. Then, insert the following XML inside each subform which defines a cell:

<occur max="-1"/>

This means that the cell subform goes from looking like this:

<subform layout="tb" name="Col3SF">
  <field name="Cell3" w="29.9999mm" h="10mm">

to looking like this:

<subform layout="tb" name="Col3SF">
  <occur max="-1"/>
  <field name="Cell3" w="29.9999mm" h="10mm">

and signifies that the cell will have one initial and minimum instance and can have as many additional instances as you need (no maximum).

Last but not least, the script!

After all that, the script is actually quite straight-forward: To add an instance of a column just add an instance of every repeatable subform cell that constitute a column. In my sample, I have a 3×3 table and each subform cell is named “Col3SF”. That means that the script looks like this (in JavaScript):


Then, to remove an instance of the column, just do the reverse: Use the Instance Manager’s removeInstance method to remove an instance of each cell subform.

Bug when adding/removing table cell instances

Of course, everything was going great until now… Unfortunately, I discovered a little snag in playing with table column instances while making this sample. Fortunately, the bug has already been fixed in Acrobat 8.


The first manifests itself when the second new instance of a column is added (by adding an instance of a column, I mean adding an instance of each cell subform in each row which collectively constitute a table column — as in my sample script above earlier). As of the second new instance, the cell in the header row will stop appearing in all subsequent instances.

There’s also an issue with removing column instances (by removing an instance of each cell subform). In this case, all new instances are removed until what was originally the first instance to be added is removed, leaving only the original, initial instance. What happens is that part of the last instance to be removed remains rendered on the form which doesn’t really look nice because it looks like the instance is still there (even though you can’t click on the cells anymore).

The problem is that the form’s layout isn’t properly updated after columns are added or removed.


Luckily, there’s the xfa.layout object which gives us a solution to this problem when version of Acrobat prior to 8.0 are used to render the form. More specifically, versions 7.0.5+ since table support didn’t appear until then, when Designer 7.1 was released.

Using the xfa.layout object, you can tell Acrobat to re-render the form at your command. This effectively repaints the entire form and gets rid of any artifacts (those being the incorrectly rendered column instances). So, after adding or removing column instances, just place the following command:


Please use this with caution, however, since it may adversely affect the performance of your form (since this statement will essentially cause the entire form to be re-rendered every time a column is added/removed). That’s why I check the version of Acrobat that’s rendering the form in my sample so that I know whether I need to apply the workaround or not.

The other workaround is simply to use Acrobat 8.0 to render the form (save is as an “Acrobat 7.0.5 Dynamic PDF Form” but open it in Acrobat 8.0). Acrobat 8.0 now properly renders all instances as they get added or removed.


Please refer to the Bug List for updated information on the version(s) affected by this bug as well as if and when it was/will be fixed.

Posted by Stefan Cameron on October 28th, 2006
Filed under Acrobat,Bugs,Instance Manager,Scripting,Tables,Tutorials

Displaying All Records from an ODBC Data Connection

So far, I’ve covered two ways of connecting forms to ODBC data sources:

  1. Connecting a Form to a Database — explains how to design a form which lets the user iterate through each record one at a time; and
  2. Selecting Specific Database Records — takes the first tutorial one step further by providing a means to specify which record(s) to view.

This time, in response to Y. Gautham’s recent comments, I’ve decided to post a little tutorial on displaying all records from an ODBC data connection for reporting purposes (as opposed to editing).

XML Schema vs ODBC Data Connections — What’s the difference?

Those of you who have been using XML Schema data connections might think this is just as easy to do but it actually involves some scripting and some knowledge of the Instance Manager. This is due to the differences in the way data is loaded between the two data connection types: XML data loaded via an XML Schema data connection is loaded completely. This allows you to use bindings like “$record.XMLSchemaDataConnection[ * ]” to bind all instances of a repeating data node to a subform and therefore cause a new instance of that subform to be generated for each instance of the repeating data. On the contrary, ODBC data connections are normally used to iterate through records and therefore only one record is loaded at any given time. Because of that, you can’t binding a repeating subform to a binding like “$record.ODBCDataConnection[ * ]” in order to get one instance per record because only one record will ever be loaded at any given time. (That’s not to say that the binding doesn’t work — it does, in fact, but you never get more than one record and therefore you never get more than one instance of the subform).

Where to start?

At this point, I’m assuming you’ve already created an ODBC data connection using the Data View palette — similar to what you may have done when following my previous ODBC data connection tutorials.

Since my goal is to display all records in an ODBC data connection, it would be nice to “hit the ground running” with some pre-canned script. The Data List Box (found in the Library palette’s Custom tab) object’s Initialize script will give me a good start because it’s already designed to iterate through records in a data connection and populate a list box with record data.

Modifying the Data List Box script

In order to list all data from all records from an ODBC data connection, I’ll need to use a container into which I can add items. One way to do this is to use a repeating subform inside a flowed container. This will let me use the repeating subform’s Instance Manager in order to add a subform for each record I find.

For my form (based on the Movie Database from my previous database tutorials), I decided to use the page subform as my record data container (and named it “MovieSF”) since it’s already in a flowed subform (that is, the root subform, named “form1” by default). In the MovieSF subform, I then placed title, showTime, category and actor fields and specified “None” as the binding for each field and the MovieSF subform. Then, I specified that it should repeat for each data item using the Binding tab in the Object palette and specified no min, max or initial count. Finally, I placed the Initialize script from the Data List Box into form1’s Initialize event.

A note on bindings

Notice that I specified a binding of “None” (which means I explicitly specified that objects should not be bound to data nodes in any data connection) for the MovieSF, title, showTime, category and actor objects using the Binding tab in the Object palette. I did this to avoid binding problems later where you might end-up with an instance of the MovieSF subform for each record but no data in the fields and this is related to implicit bindings attempting to execute on each instance (or explicit binding if you explicitly specified which data node an object should be bound to).

Making the script look for the right data

The first step in modifying form1’s Initialize script (based on the Data List Box’s Initialize script) is to make sure it’s looking for the right data nodes. This is a little difficult to explain without using a diff tool so you’ll have to check-out my sample form (linked later in this post) to see it in detail. I will, however, highlight the main point of modification for this step which is labeled “Find the data nodes” in the script:

var oTitleDataNode = null;
var oShowTimeDataNode = null;
var oCategoryDataNode = null;
var oActorDataNode = null;

for (var nColIndex = 0; nColIndex < oRecord.nodes.length; nColIndex++)
  if (oRecord.nodes.item(nColIndex).name  "title")
    oTitleDataNode = oRecord.nodes.item(nColIndex);

  if (oRecord.nodes.item(nColIndex).name  "showTime")
    oShowTimeDataNode = oRecord.nodes.item(nColIndex);

  if (oRecord.nodes.item(nColIndex).name == "category")
    oCategoryDataNode = oRecord.nodes.item(nColIndex);

  if (oRecord.nodes.item(nColIndex).name == "actor")
    oActorDataNode = oRecord.nodes.item(nColIndex);

Notice how I’ve added a couple of objects and changed the contents of the For loop to look for each type of data node I need (and which is mapped using the MovieDataConn data connection).

Generating MovieSF instances for each record

This is the brains of the script which generates a new MovieSF subform instance for each record found in the MovieDataConn data connection. This is done using the “_MovieSF” Instance Manager:

  // Create a new instance and get a reference to it.
  var oNewMovie = _MovieSF.addInstance(0);

  // Populate the fields inside the new instance.
  oNewMovie.title.rawValue = oTitleDataNode.value;
  oNewMovie.showTime.rawValue = oShowTimeDataNode.value;
  oNewMovie.category.rawValue = oCategoryDataNode.value; = oActorDataNode.value;

  // Move to the next record in the data connection,
  //  thereby causing all data node references to be
  //  updated accordingly.;

You should take note of how I save a reference to the new MovieSF subform instance into a local variable which I can then use to populate its fields using the appropriate data nodes. Also, if you’re wondering why I’m specifying zero as the parameter for the addInstance function, here’s why (in short, because I don’t want to merge the new instance of the MovieSF subform with data).

The goods

If you’re curious to see how my sample form works, here it is:

Download Sample [zip]

Minimum Requirement: Designer 7.0, Acrobat Standard 7.0.

Don’t forget to create a System DSN named “FormBuilderDB” using the included SQL file.

Updated: October 17, 2006

Posted by Stefan Cameron on October 12th, 2006
Filed under Data Binding,Instance Manager,Scripting,Tutorials

Demystifying IM.AddInstance

The definition for the Instance Manager’s addInstance method is as follows:

addInstance( [BOOLEAN param] )

Personally, I find the word param a little vague. I think it should be called merge instead because that would give a clearer indication as to what it stands for: Essentially, if the data you’ve merged into your form has a repeating section that you’ve bound to a repeating (dynamic) subform and not all instances of this repeating data section have been merged into the form’s layout, you can control whether the new instance of the dynamic subform pertaining to that repeating data section will get merged with the next section or not by specifying true (merge — the default) or false (don’t merge — show empty instance) as the parameter value.

Usually, this doesn’t make a difference because you typically merge all instances of a repeating data section into your form and once there are no more data instances to merge, addInstance(true) will yield the same results as addInstance(false): an new empty (no data merged-in) instance.

Consider, however, the case where your form is a report and you’d like to show only a glimpse of the data instead of loading all 2000 instances of a repeating section. If your data was sorted from the most important to the least important, you could significantly improve the performance of your report (with respect to load time) by limiting the number of instances of that repeating data section that are initially merged into your form. Once your form is loaded, it could provide ways for the reader to get more instances if they wish to do so.

This can be achieved by using the Max property on the dynamic subform’s Binding tab in the Object palette along with addInstance(true).

Here’s a sample which has a data connection to an XML Data File that lists movies. There are 16 movies in total but the form limits the number of movies initially displayed to 10 and provides a Show More button. When this button is pressed, the movie dynamic subform’s Max count property, initially set to 10, is incremented by 1 and a new movie instance is added using true as the parameter.

Download Sample [zip]

Minimum Requirements: Designer 7.0, Acrobat 7.0.

Note: If you open the form in Acrobat, don’t forget to import the data into it using the “File | Form Data” menu.

Posted by Stefan Cameron on July 8th, 2006
Filed under Instance Manager,Scripting,Tutorials

Remove, Remerge

There’s a bug currently logged against Acrobat 7.x where removing an instance of a dynamic subform, using the Instance Manager (IM)’s removeInstance(int) method, doesn’t cause an update to the IM’s count of currently instantiated subforms.

OK, so maybe that was a little too technical so I’ll try to simplify: In Acrobat 7.x, when you remove an instance of a dynamic subform using the IM’s removeInstance(int) method and then check the number of remaining instances using the count property, the number you’ll get won’t reflect the number that remains.

Adobe is aware of this bug and will hopefully be providing a fix for it in an up-coming release.

Fortunately, there’s a simple work-around (and even if the bug gets fixed in a future release, you should probably be checking the version of Acrobat that’s running your form to determine whether you need to be using the work-around or not):


// Force a remerge of the form's current data set with its template
//  to cause an update to the "count" property of all IMs

Calling the Form object’s remerge() method will “force the remerging of the data model and template model to re-create the form model”, as explained in the Adobe XML Form Object Model Reference. This means that the form’s current data set will be remerged with the template (the form objects like dynamic subforms, fields, etc.). The result will be a form that looks exactly the same as it did in its state just prior to calling xfa.form.remerge() but with all IMs properly updated to the current number of dynamic subforms which they’re managing, thus correctly updating each IM’s count property.

Even if this problem is addressed in a future release, you’ll want to check the version of Acrobat that’s running your form in order to know whether it has the fix or not (in JavaScript as follows):

// get the host's version as a string and split it into an array
var oVerArray =".");

if (oVerArray[0] == "7")

Or more simply:

if (".")[0] == "7")

Posted by Stefan Cameron on May 25th, 2006
Filed under Instance Manager,Scripting

Add, Recalculate

Here’s a little something that very important to know when working with dynamic subforms and using their Instance Managers (IMs) to add instances of them to a form: New subform instances aren’t automatically incorporated into the form’s calculations!

You would immediately notice this problem if you had a form which calculated a total based on line items which can be added or removed from the form. When you add a new line item using the IM’s addInstance(bool) method, the grand total of, say, the cost of all line items isn’t updated to reflect the data you enter into the new line item. This is because the new line item hasn’t been made part of the form’s set of calculation dependencies and is therefore not accounted for by your “grand total” calculation. As a matter of fact, until a call to xfa.form.recalculate() is made, none of the new instances added will be included in the form’s calculations.

To demonstrate this, I’ve created a sample form which has a “line item” section to which line items can be added. As line items are added and their costs changed, the grand total fields at the bottom calculate the total cost of the order: One grand total field performs its calculation using the FormCalc SUM function and a SOM Expression identifying the collection of fields to total while the other uses the LineItem dynamic subform’s IM object to calculate the grand total. Finally, there’s a check box at the top of the repeating “line item” section which, when checked, will cause the “Add Item” button to execute the xfa.form.recalculate(true) statement after adding a new line item. To see the difference, play around with the form by adding line items with the check box both checked and unchecked.

Note that this issue was addressed in Acrobat/Reader 8.0. Therefore, if your form targets this version (or later) of Acrobat/Reader, you shouldn’t need the recalculate() workaround.

Download Sample [zip]

Minimum Requirements: Designer 7.x, Acrobat 7.x.

Updated Nov 19, 2009 — Added note about the issue being resolved in Acrobat/Reader 8.0+.

Posted by Stefan Cameron on May 20th, 2006
Filed under Instance Manager,Scripting,Tutorials