“No Primary Key item has been defined for form region”

Otherwise reported as “WWV_FLOW_FORM_REGION.NO_PRIMARY_KEY_ITEM” or merely “Internal error”, this bug caused me to waste hours of investigation, twice, because a simple Google search was not returning any results. This post is merely to remedy that situation.

On an APEX 19.1 page with a new Form region combined with an Interactive Grid region, when the user makes a change to a record and Submits the page, they get this error.

This is caused by bug 29612553 – FORM REGION DML PROCESS THROWS INTERNAL ERROR WHEN INTERACTIVE GRID DML PROCESS IS ON THE SAME PAGE and fixed by APEX patch 29369869.


Menu Popup with Declarative List

In the past when I’ve needed to add half a dozen or more buttons to a page, I’ve sometimes encased them in a Collapsible region so that the user can slide them out of the way instead of clogging up the screen. Recently however I’ve started (sparingly) using a Menu Popup, as per this tutorial. The issue I have with this method, however, is that the menu items are defined in a shared component (a List) which means it’s not defined on a per-page basis.

Some of the actions simply need to do a Submit on the page, which is simple enough: set the URL Target to something like:

In other cases, the action needs to do something more specific to the page, e.g. show a region:

apex.theme.openRegion("popupQuestion")

Or the action might need to navigate to another page, passing parameters based on specific items on the page. This means the list, defined in Shared Components, now has hardcoded elements that are only useful for that one page; more to the point, they are defined outside of the page – I’d rather that everything specific to a page is defined within that page’s definition.

The approach I’m using now is to use a custom trigger. Each list item has its URL Target set to something like:

The third parameter is set to a unique code that the page can use to identify which menu option was chosen. This parameter will be passed to this.data in the custom trigger’s event handler.

On the page, I have a Dynamic Action with the following attributes:

  • Event: Custom
  • Custom Event: menuAction
  • Selection Type: JavaScript Expression
  • JavaScript Expression: document
  • True Action: Execute JavaScript Code, e.g.:
switch(this.data) {
  case 'OPEN_POPUP':
    apex.theme.openRegion("popupQuestion");
    break;

  default:
    apex.submit({request:this.data,showWait:true});
}

Note that to do a simple Submit on the page, all I need to do is set the request on the third parameter of the menu item’s URL. If I want to do something slightly different for a particular request, I can put an extra “case” in the JavaScript code to handle it.

The benefit of this approach is that this trigger becomes the jumping-off point for all such menu actions for this page. In theory I could re-use the same List on multiple pages (if the items in the list are generic enough) but have different behaviour occur for each menu item specific to each page. The only challenge with this approach might be if you needed some conditions on each menu item, e.g. so they are shown or hidden in specific circumstances. If the condition for a menu item references a particular page item the List will no longer be generic and re-usable. For this reason, I usually still use a separate List for each menu for each page.

Perhaps in a future release of APEX we will gain the ability to define a List on a Page instead of in Shared Components. In the meantime, if you are interested in all the details on this method (including a solution for implementing a redirect to another page, or to open a modal page), refer to this tip.

EDIT 22/8/2019: Thanks to Robert Gerstein who noticed an issue with this solution when using Internet Explorer. A workaround for this is to not call apex.event.trigger directly in the URL on the list item, but to call a function instead (refer to comments below).


Conditionally Required Floating Item

An item in the Universal Theme using the Optional – Floating template looks like this:

An item using the Required – Floating template looks like this:

In addition, if the item is required we would most probably set the Value Required attribute to Yes. What if the item is sometimes required but not always? How do we create a Conditionally Required field?

Firstly, we would make sure there is a Validation on the field that checks that the value is provided if required. This way, regardless of what the form may or may not send to the database, it is validated appropriately.

Secondly, to indicate to the user that the item is required or optional, based on the value of another item, we can use a Dynamic Action that sets the required item property (this triggers the client-side validation) and adds or removes the is-required class from the item’s container (this shows the little red “required” indicator on the page).

For example, let’s say that whether item P1_COST_CENTRE is required or not is dependent on whether a hidden item, P1_COST_CENTRE_REQUIRED, has the value 'Y'.

  • Create a Dynamic Action
    1. Event: Change
    2. Selection Type: Item(s)
    3. Item(s): P1_COST_CENTRE_REQUIRED
    4. Client-side Condition Type: Item = Value
    5. Item: P1_COST_CENTRE_REQUIRED
    6. Value: Y
  • Create a True Action: Execute JavaScript Code
var item = $("#P1_COST_CENTRE");
item.prop("required",true);
item.closest(".t-Form-fieldContainer").addClass("is-required");
  • Create a False Action: Execute JavaScript Code
var item = $("#P1_COST_CENTRE");
item.prop("required",false);
item.closest(".t-Form-fieldContainer").removeClass("is-required");

The above code works for all item templates (“Optional”, “Optional – Above”, “Optional – Floating”, etc.) in the Universal Theme; I’ve tested this on APEX 18.2 and 19.1.

Note: this is custom code for the Universal Theme, so it may or may not work for other themes; and might stop working in a future revision of the theme.

Plugins

UPDATE 29/7/2019: I’ve created some simple Dynamic Action plugins (for APEX 18.2 and later) to implement this, if you’re interested you can download them from here:

To use these plugins, select them as an Action to take on a Dynamic Action:

EDIT 29/7/2019: modified to use a better method to find the container div.

Older Themes

In other themes, the way that a required field is rendered is different. For example, in Theme 26 (Productivity Applications) the label for a required item is rendered in bold, along with a red asterisk; if the item is optional, no red asterisk is rendered. The way to make an item conditionally mandatory in this theme is:

  1. Set the item to use the Required template (so that the red asterisk is rendered).
  2. In the Dynamic Action JavaScript, execute the following if the item should be optional:
var itemLabel = $("label[for='P1_COST_CENTRE']");
itemLabel.removeClass("uRequired");
itemLabel.addClass("uOptional");

To make the item required again:

var itemLabel = $("label[for='P1_COST_CENTRE']");
itemLabel.removeClass("uOptional");
itemLabel.addClass("uRequired");

Report Google Map Plugin v1.0 Released

Over the past couple of weeks I’ve been working on an overhaul of my Google Maps region for Oracle Application Express. This free, open-source plugin allows you to integrate fully-featured Google Maps into your application, with a wide range of built-in declarative features including dynamic actions, as well as more advanced API routines for running custom JavaScript with the plugin.

The plugin has been updated to Oracle APEX 18.2 (as that is the version my current system is using). Unfortunately this means that people still on older versions will miss out, unless someone is willing to give me a few hours on their APEX 5.0 or 5.1 instance so I can backport the plugin.

EDIT: Release 1.0.1 includes some bugfixes and a backport for APEX 5.0, 5.1 and 18.1.

The plugin is easy to install and use. You provide a SQL Query that returns latitude, longitude, and information for the pins, and the plugin does all the work to show them on the map.

The plugin has been rewritten to use the JQuery UI Widgets interface, at the suggestion of Martin D’Souza. This makes for a cleaner integration on any APEX page, and reduces the JavaScript footprint of each instance on the page if you need two or more map regions at the same time. This represented a rather steep learning curve for me personally, but I learned a lot and I’m pleased with the result. Of course, I’m sure I’ve probably missed a few tricks that the average JavaScript coder would say was obvious.

The beta releases of the plugin (0.1 to 0.10) kept adding more and more plugin attributes until it hit the APEX limit of 25 region-level attributes. This was obviously not very scaleable for future enhancements, so in Release 1.0 I ran the scythe through all the attributes and consolidated, replaced, or removed more than half of them – while preserving almost every single feature. This means v1.0 is not backwards compatible with the beta versions; although many attributes are preserved, others (including the SQL Query itself, which is rather important) would be lost in the conversion if the plugin was merely replaced. For this reason I’ve changed the Internal ID of the plugin. This is so that customers who are currently using a beta version can safely install Release 1.0 alongside it, without affecting all the pages where they are using the plugin. They can then follow the instructions to gradually upgrade each page that uses the plugin.

All of the plugin attributes relating to integrating the plugin with page items have been removed. Instead, it is relatively straightforward to use Dynamic Actions to respond to events on the map, and an API of JavaScript functions can be called to change its behaviour. All of this is fully documented and sample code can be found in the wiki.

New features include, but are not limited to:

  • Marker Clustering
  • Geo Heatmap visualisation (this replaces the functionality previous provided in a separate plugin)
  • Draggable pins
  • Lazy Load (data is now loaded in a separate Ajax call after the page is loaded)

The plugin attributes that have been added, changed or removed are listed here.

If you haven’t used this plugin before, I encourage you to give it a go. It’s a lot of fun and the possibilities presented by the Google Maps JavaScript API are extensive. You do need a Google Maps API Key which requires a Google billing account, but it is worth the trouble. It is recommended to put a HTTP Referer restriction on your API Key so that people can’t just copy your public key and use it on their own sites. For more information refer to the Installation Instructions.

If you are already using a beta version of the plugin in your application, please review the Upgrading steps before starting. Don’t panic! It’s not quite as simple as just importing the plugin into your application, but it’s not overly complicated. If you were using any of the Page Item integration attributes, you will need to implement Dynamic Actions to achieve the same behaviour. If you had any JavaScript integrations with the plugin, you will need to update them to use the new JQuery UI Widget API calls. I am keen for everyone to update to Release 1.0 as soon as possible, so I will provide free support (via email) for anyone needing help with this.

I am very keen to hear from everyone who is using the plugin, and how it is being used – please let me know in the comments below. If you notice a bug or have a great idea to enhance the plugin, please raise an issue on GitHub.

Links


Change Item Icon Dynamically

The floating item type has an optional “Icon” property that allows you to render an icon next to the item, which can help users quickly identify what the item is for. This is especially helpful when the form has a lot of items.

The icon attribute can be static, e.g. fa-hashtag, or it can be chosen based on the value of another item, e.g. &P1_FA_ICON..

If you want the icon to change dynamically as the user enters or modifies data, it’s a little bit more complicated. I have a list item based on a table of asset categories, and each asset category has an icon assigned to it. When the user selects an asset category from the list I want it to get the icon from the table and show it in the item straight away.

To do this, I use two Dynamic Actions: (1) a PL/SQL action which updates the hidden Pn_FA_ICON item, and (2) a Javascript action which manipulates the displayed icon next to the list item.

This is my item and its two dynamic actions.
The Icon attribute causes the icon to be shown when the page is loaded.

The Execute PL/SQL Code action is a simple PL/SQL block which gets the icon from the reference table for the selected category code. Make sure the “Wait for Result” is “Yes”, and make sure the Items to Submit and Items to Return are set to P260_CATEGORY_CODE and P260_CATEGORY_FA_ICON, respectively.

select x.fa_icon
into   :P260_CATEGORY_FA_ICON
from   asset_categories x
where  x.code = :P260_CATEGORY_CODE;

On examining the source of the page, we see that the select item is immediately followed by a span which shows the icon:

The Execute JavaScript Code action finds the item (in this case, the triggering element), then searches the DOM for the following span with the apex-item-icon class. Once found, it resets the classes on the span with a new set of classes, including the new icon.

It’s a little gimmicky but it’s an easy way to delight users, and it might help them to quickly identify data entry mistakes.

Warning: due to the way the javascript manipulates the DOM, this method is not guaranteed to work correctly in future releases of APEX., so it will need to be retested after upgrades.


“Before Header” Branch

It’s well known that after processing a page one often needs to add a Branch so the user is taken to another page, e.g. to start the next step in a process. It’s less common to need a Branch that is evaluated before the page is shown. This is a “Before Header” Branch and I use it when the user might open a page but need to be redirected to a different one.

A good example is a page that is designed to direct the user to two or more different pages depending on what data they requested.

Another way that a branch like this can be useful is where a user might navigate to a page that should show a record, but if the record ID is not set, I might want the page to automatically redirect the user back to a report page instead.

Of course, you have to take some care with these sorts of branches; if the target page also has its own “Before Header” branch, that will also be evaluated; if the user ends up in a loop of branches the page will fail to load (with a “ERR_TOO_MANY_REDIRECTS” error).

This is the order in which various steps are done before APEX shows a page:

  1. Authentication check
  2. Verify session
  3. “Before Header” Branches
  4. Authorization check
  5. Computations
  6. “Before Header” Processes
  7. Regions, etc.

One of the implications of the above order is that any computations or processes that set or change application state (e.g. an application item) are not run before it evaluates conditions or attributes for any “Before Header” Branches. This applies regardless of whether the computations or processes are defined on the page, or defined globally in Shared Components. This little detail tripped me up today, because I had a branch that I needed to run based on a condition that relied on state that should have been set by a “Before Header” process defined globally.

If you need to redirect a user to a different page on the basis of any application state that is set by a computation or process, you can use a PL/SQL Process instead that does the redirect. The PL/SQL code to use is something like:

apex_util.redirect_url(p_url => apex_page.get_url(p_page => 1));

Warning: redirect_url raises the exception ORA-20876: Stop APEX Engine, so it’s probably preferable to avoid combining this with other PL/SQL code that might need to be committed first.


Showing image thumbnails in Icon View

I had an interactive report an an old APEX application that I’ve kept maintained for quite a few years, which is able to show an Icon View that shows a thumbnail of the image for each item.

The problem was that the layout sometimes went wonky depending on the size of the image or the size of the label text. How the items were laid out depended on the width of the viewing window as well. I have set Columns Per Row to 5, and I’m using a Custom Icon View with the following Custom Link:

<a href="#WORK_URL#">
<img src="#IMAGE_URL#" width="140px">
<p>
#FULL_TITLE_SORT#
</a>

Each item shows an image, scaled down to width 140 pixels (my images come in all sorts of sizes), plus the title; either the title or the image may be clicked to open the details for it.

This is how it looked:

Depending on a number of variables (length of the label text, and the width of the viewing window) some rows would show their first item in the 5th column instead of over on the left; this would have a run-on effect to following rows. In addition, I wasn’t quite happy with the left-justified layout for each item.

To fix this I added some DIVs and some CSS. My Custom Link is now:

<div class="workcontainer">
  <div class="workicon">
    <a href="#WORK_URL#">
      <img src="#IMAGE_URL#" class="workimg">
    </a>
  </div>
  <div class="worktitle">
    <a href="#WORK_URL#">#FULL_TITLE_SORT#</a>
  </div>
</div>

Each record gets a container div, within which are nested a div for the image and a div for the label.

The width attribute is no longer needed directly on the img; instead, I added the following CSS to the region Header Text:

<style>
.workcontainer {
    text-align:center;
    width:160px;
    height:200px;
  }
.workicon { display:block; }
.workimg {
    max-width:160px;
    max-height:160px;
    width:auto;
    height:auto;
  }
.worktitle {
    display:block;
    font-weight:bold;
    height:40px;
    overflow:hidden;
  }
</style>

Some of the key bits here are that the container div has width and height attributes, and the image is constrained using max-width, max-height, width:auto and height:auto. Also, the work title is constrained to a 40 pixel high block, with overflow:hidden.

My report now looks like this:

The images are scaled down automatically to fit within a consistent size, and both the images and the labels are horizontally centered leading to a more pleasing layout. If an image is already small enough, it won’t be scaled up but will be shown full-size within the available area. Also, the label height is constrained (if an item label is too high the overflow will be hidden) which solves the layout problem I had before. If the image is not very tall, the label appears directly beneath it which is what I wanted.

The only remaining issue is that the icon view feature of the interactive report generates a table with rows of a fixed number of columns (5, in my case), which doesn’t wrap so nicely on a small screen when it can’t fit 5 in a row. I’ve set Columns Per Row to 1 now, and it seems to wrap perfectly; it shows up to a maximum of 6 items per row depending on the viewing window width.

POSTSCRIPT – Lazy Load

Thanks to Matt (see comment below) who pointed out that a report like this would benefit greatly from a Lazy Load feature to reduce the amount of data pulled to the client – for example, if the user requests 5,000 records per page and starts paging through the results, each page view could potentially download a large volume of data, especially if the images are quite large.
I’ve implemented this now and it was quite straightforward:

  1. Download the latest release of the jQuery plugin “Lazyload Anyhttps://github.com/emn178/jquery-lazyload-any
  2. Upload the file jquery.lazyload-any.js to Static Application Files
  3. Add the following to the page attribute File URLs:
    #APP_IMAGES#jquery.lazyload-any.js
  4. Add a Dynamic Action to the report region:
    Event = After Refresh
    Action = Execute JavaScript Code
    Code = $(".workicon").lazyload()
    Fire on Initialization = Yes
  5. Modify the Icon View Custom Link code to put the bits to lazy load within a script tag of type “text/lazyload” (in my case, all the html contents within the “workicon” div), e.g.:
<div class="workcontainer">
  <div class="workicon">
    <script type="text/lazyload">
      <a href="#WORK_URL#">
        <img src="#IMAGE_URL#" class="workimg">
      </a>
    </script>
  </div>
  <div class="worktitle">
    <a href="#WORK_URL#">#FULL_TITLE_SORT#</a>
  </div>
</div>

This was an important addition in my cases as some of the images were quite large; I don’t have to worry about load on my server because they are hosted on Amazon S3, but I do have to pay a little bit for the transfer of data.


Autoformat Numbers in an Interactive Grid

A lot of the applications I build allow users to enter large numbers of monetary amounts, and the way these numbers are presented can have an impact on how easy it is for them to read and check those numbers.

All such amounts are formatted for display using a system-wide standard format (in our case, the Australian standard fm999g999g999g990d00), with any amounts less than $0.01 rounded to the nearest cent. After an amount is entered or modified, the user expects to see the value formatted correctly straight away; so I use javascript to take their entered value, convert it to a number, format it and set its value back in the field. Also, if the user has copied in any non-numeric characters (e.g. a $ symbol), these are simply removed silently.

An interactive grid (this one was a work in progress) with some editable monetary amounts.

In the past I had a global javascript file which I’d load with each application with the following basic functions to auto-format any monetary amount fields as the user tabs out of them, whether they appear in an ordinary form or a tabular form:

Number.prototype.formatMoney = function(decPlaces, thouSep, decSep) {
/* this function taken from http://stackoverflow.com/questions/9318674/javascript-number-currency-formatting */
  var n = this,
  decPlaces = isNaN(decPlaces = Math.abs(decPlaces)) ? 2 : decPlaces,
  decSep = decSep == undefined ? "." : decSep,
  thouSep = thouSep == undefined ? "," : thouSep,
  sign = n < 0 ? "-" : "",
  i = parseInt(n = Math.abs(+n || 0).toFixed(decPlaces)) + "",
  j = (j = i.length) > 3 ? j % 3 : 0;
  return sign + (j ? i.substr(0, j) + thouSep : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + thouSep) + (decPlaces ? decSep + Math.abs(n - i).toFixed(decPlaces).slice(2) : "");
};

function parseNumeric(v) {
  //strip any non-numeric characters and return a non-null numeric value
  return parseFloat(v.replace(/[^\d.-]/g,''))||0;
}

$(document).ready(function() {
  //automatically format any item with the "edit_money" class
  $( document ).on('change', '.edit_money', function(){
    var i = "#"+$(this).attr("id"), v = $(i).val();
    if(v){ $(i).val( parseNumeric(v).formatMoney() ); }
  });
});

I would then simply add the class edit_money to any item in the application and it would automatically apply the formatting; for example, if the user types in 12345.6, it changes the value to 12,345.60.

TL;DR
If you want to skip to the punchline, scroll down past the next few paragraphs where I take you down a merry rabbit-hole that, as it turns out, was completely unnecessary (but still somewhat educational).

Now we’re on APEX 19.1 and starting to use Interactive Grids (IG) for a lot of new screens, but applying the edit_money class to the columns in the grid doesn’t work, because the edit item that is generated on-the-fly by the grid doesn’t [edit: I was wrong here] conform to the structure expected by my document-on-change function callback.

Instead, to solve this I decided to add a single dynamic action to the IG that sets the value to a JavaScript Expression which calls my parseNumeric and formatMoney functions.

Aside: when Google failed me
It took me a little bit of searching and experimentation to work out what the JavaScript Expression should be; I didn’t expect it to be complex, and knew it should refer to the item without specifying any particular column name or ID, because this DA could be triggered from multiple columns in the same grid. But I just didn’t know how to refer to the “current item”, and the attribute help was not as helpful as I’d have liked. My google-fu was failing me as well (although I picked up a few neat tricks that I’d like to try in future); I tried searching “oracle apex interactive grid javascript expression” but most of the results were for complicated scenarios that didn’t apply to what I thought was this simple case. I even tried reading the Oracle documentation but just couldn’t find what I was looking for.

I guessed the JavaScript Expression would have access to a this object that should give me access to the item’s value. I used a little trick to copy this into a global variable and used the Chrome debug console to examine this to see how to get the value of the cell being edited. Firstly, in the page Function and Global Variable Declaration I added var x;. Secondly, in the JavaScript Expression on the dynamic action I entered x=this. Running the page, I entered a value into the cell in the grid, opened the Chrome console, then typed “x”. Chrome immediately showed the structure of “x”:

That “triggeringElement” looks like it might be what I’m after, so I continued typing:

After finishing typing “.val()” it gave an error “val is not a function”. I’d seen other code around the place that converts triggeringElement to a jQuery object, so I tried that instead:

This spat out the number I’d entered. So initially I used $(this.triggeringElement).val(). Later I did some more digging and realised I didn’t need jQuery here, I can use the value attribute directly – this.triggeringElement.value. I suspect this is one of those basic things that they teach you on day one of an “Intro to APEX Interactive Grids 101” class but I must have been sick that day 🙂

My final DA has the following attributes:

  • Event = Change
  • Selection Type = Column(s)
  • Region = [the interactive grid region]
  • Column(s) = [list of all the editable monetary columns]
  • Action = Set Value
  • Set Type = JavaScript Expression
  • JavaScript Expression =
    this.triggeringElement.value?parseNumeric(this.triggeringElement.value).formatMoney():""
  • Suppress Change Event = Yes
  • Selection Type = Triggering Element
  • Fire on Initialization = No
Dynamic action attributes
DA True Action attributes

It’s not quite as simple as adding the class to all the items, but at least it’s just one dynamic action that I need to add to each interactive grid.

POSTSCRIPT
As pointed out by John, I went down this rabbit hole for one simple and annoying reason: I forgot that there are not one, but twoCSS Classes” attributes on each item, and I’d put my “edit_money” class in the wrong attribute.

This may have the appearance of being the right one (it’s the first one listed). This is not the CSS Classes you’re looking for.
This is the CSS Classes you’re looking for.

Escaped strings and PL/SQL Dynamic Actions

I had a simple form where the user can select a vendor from a select list (using the Select2 plugin), and the form would retrieve the latest purchase details based on a simple string search of that vendor’s name – for most cases. Sometimes, however, it failed to find anything even though I knew the data was there.

There was a dynamic action that fires on Change of the list item that executes a PL/SQL procedure and retrieves the Total Amount and the Memo:

transaction_pkg.get_suggestion
  (vendor_name => :P5_VENDOR_NAME
  ,total_amt   => :P5_AMOUNT /*out*/
  ,memo        => :P5_MEMO); /*out*/

This didn’t work in some cases where a vendor name included special characters, such as &. This is because the item had Escape special characters set to the default (Yes), which is good practice to protect against Cross-Site Scripting (XSS) attacks. Therefore, the value sent by the dynamic action to my PL/SQL procedure had the special html characters escaped, e.g. “Ben & Jerry’s” was escaped to “Ben &amp; Jerry&#x27;s“. I believe APEX uses the apex_escape.html function to do this.

Usually, I would try to rework my code to send a numeric ID instead of a string; but in this particular case the data model does not have surrogate keys for vendors (it’s just a free-text field in the transactions table) so I want to use the name.

If I was doing this properly, I would fix the data model to make vendors first-class entities, instead of using a free-text field. This would allow using a surrogate key for the vendor list and this escaping behaviour would no longer be a problem.

Another alternative here is to use the latest transaction ID as a surrogate key for each vendor; but then I would need to modify the form to translate this back into a vendor name when inserting or updating the table; and this would add unnecessary complexity to this simple form, in my opinion.

Instead, before sending this string to my procedure, I’ve chosen to unescape the data. To do this, I add a call to utl_i18n.unescape_reference:

transaction_pkg.get_suggestion
  (vendor_name => utl_i18n.unescape_reference(:P5_VENDOR_NAME)
  ,total_amt   => :P5_AMOUNT /*out*/
  ,memo        => :P5_MEMO); /*out*/

This converts the escaped data back into a plain string, and my simple data matching procedure now works as expected.


Form Regions – Superclass/Subclass

The new Form Region feature introduced in Oracle APEX 19.1 is a big improvement to the way that single-record forms are defined declaratively.

In prior versions of APEX, you were effectively limited to a single DML load process and a single DML submit process, and all the items on the page that were linked to a table column were required to be from only a single table. If you wanted to do anything more complicated than that, you had to either split your form into multiple pages or get rid of the DML processes and hand-code the PL/SQL yourself.

The new components/attributes for Form Regions are:

  • Region type “Form” which defines the Source Table (or view, or SQL Query, or PL/SQL returning a SQL query, or Web Source) and associated semantics.
  • Item Source attribute that associates each item with a particular Form Region. The item can optionally be marked as “Query Only” and/or as a “Primary Key”.
  • Pre-render process type “Form – Initialization” that is associated with a Form Region.
  • Page process type “Form – Automatic Row Processing (DML)” that is associated with a Form Region. This can be used to change the Target for the form region (default is the Source Table) to a different table or view, or to replace the DML processing with your custom PL/SQL. You can also modify other semantics such as Prevent Lost Updates and row locking.

If you generate a single-record form page APEX will generate all the above for you and you can then customise them as you need.

Now, I want to create a slightly more complex form – one based on two tables that are related – “Transaction Lines” and “Reserve Lines” have the same Primary Key, and a referential integrity constraint linking them. They act like a “super class / subclass”, where one table (“Reserve Lines”) is optional. This data model eliminates the need to have lots of nullable columns in a base table.

Data model

Here’s the form for editing a single “Transaction Line”:

Form with “Reserve” unticked

The form shows the associated “Reserve Line” if it exists:

Form with “Reserve” ticked

If the “Reserve” checkbox is ticked, the Reserve details region is shown and the user can enter the Reserve Line attributes.

I need the page to perform the following actions:

  1. For a new record, if the user leaves “Reserve” unticked, only a Transaction Line should be inserted.
  2. For a new record, if the user ticks “Reserve”, both a Transaction Line and a Reserve Line should be inserted.
  3. For an existing record, if the user ticks or unticks “Reserve”, the Reserve Line should be inserted or deleted accordingly.

If you want to see this example in action, feel free to try it out here:
https://apex.oracle.com/pls/apex/f?p=JK201904&c=JK64 (login using your email address if you want). The starting page is a blank transaction; click “Create”, then click “Add Line” to open the transaction line page.

The page is composed of two Form Regions. Note that in this example I’ve laid out all the items for each form within its Form Region, but this is not strictly necessary.

To do this, I built the form in the following manner:

  1. Created a Form Region for the Transaction Line with standard Initialize form and Automatic Row Processing (DML) processes.
  2. Created a second Form Region for the Reserve Line with the standard processes (but customised later).
  3. Added the “P2_RESERVE_Y” checkbox item, not linked to any source column. Added a dynamic action to show/hide the Reserve details region if it is ticked/unticked.
  4. Added a “set up reserve line” PL/SQL Code process immediately after the Initialize form Transaction Line and just before the Initialize form Reserve Line process:
  • Server-side Condition Type = Rows returned
  • SQL Query =
    select null from reserve_lines where line_id=:P2_LINE_ID
  • PL/SQL Code:
:P2_RESERVE_LINE_ID := :P2_LINE_ID;
:P2_RESERVE_Y := 'Y';

5. Change the Automatic Row Processing (DML) for the Reserve Line region:

  • Target Type = PL/SQL Code
  • PL/SQL Code to Insert/Update/Delete:
case when :P2_RESERVE_Y is null then

  delete reserve_lines where line_id=:P2_RESERVE_LINE_ID;

when :P2_RESERVE_Y is not null
and :P2_RESERVE_LINE_ID is null then

  insert into reserve_lines
    (line_id,asset,target_amt,target_year)
  values
    (:P2_LINE_ID,:P2_ASSET,:P2_TARGET_AMT,:P2_TARGET_YEAR )
  returning line_id into :P2_RESERVE_LINE_ID;

when :P2_RESERVE_Y is not null
and :P2_RESERVE_LINE_ID is not null then

  update reserve_lines
    set asset=:P2_ASSET
       ,target_amt=:P2_TARGET_AMT
       ,target_year=:P2_TARGET_YEAR
  where line_id=:P2_RESERVE_LINE_ID;

else
  null;
end case;

6. Add a special handler to delete the reserve line if the user clicks the Delete button (this needs to be executed prior to the Process form Transaction Line to avoid a FK violation).

This solution is not quite as “low-code” as I’d like; it would be simpler to call a TAPI here instead of hardcoding the DML statements. The reason we need custom PL/SQL here is that when the user clicks the “Create” or “Save” buttons (which are associated with the SQL Insert and Update actions, respectively), we often need to translate this into a different DML action (insert, update, or delete) for the Reserve Lines table.