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How to create client side callout onchange function



This howto discusses how to implement client side (javascript) functions which are executed when a field value in the user interface changes. The onChange concept corresponds to the traditional callout, the main difference is that the onChange functionality is implemented on the client. This gives the following advantages:

In addition the onChange function has all the benefits of the classic callout, you can still call the server to execute more performance intensive actions or do queries.

Example Module

This howto is supported by an example module which shows examples of the code shown and discussed.

The code of the example module can be downloaded from this mercurial repository:

The example module is available through the Central Repository (See 'Client Application Examples'), for more information see the Examples Client Application project page.

Defining OnChange Functions

An OnChange function is a function in javascript available through a global ID. The global ID should be unique, it is strongly adviced to use the module's db prefix. The OnChange function has to be defined in a javascript file located in the module, see here for information on howto add javascript code to Openbravo.

Here is an example of an OnChange function defined in the example module:

OB.OBEXAPP.OnChangeFunctions = {};
OB.OBEXAPP.OnChangeFunctions.Note_Name = function(item, view, form, grid) {
  // set a message
  view.messageBar.setMessage(isc.OBMessageBar.TYPE_INFO, 'Changed!', 'You changed the name to ' + item.getValue());
  // set the value for the description and make sure that the
  // onchange handlers are called
  form.setItemValue('description', 'Description ' + item.getValue());

As you can see the OnChange function is placed in a global object, in this case the module's dbprefix is used for that. It is important to note that you should not use var before the global object definition, otherwise your var is not global. This is because the global javascript code included in Openbravo is in fact executed within a function.

An onchange function receives 4 arguments:

This example onchange sets a message in the message bar and sets the value of another field. Note that the form's setItemValue method is used to trigger other onchange functions. The form also has a setValue method but that one will not trigger an onchange event.

If your onchange function does not work or is not called or if your window does not load anymore after defining an onchange then check the console.

Registering, setting an OnChange for a specific field

There are two ways to link an OnChange function to a specific field:

The first approach allows you to define the OnChange directly in the Field definition. For the second approach you need to use javascript, but it offers additional flexibility.

Setting an OnChange function through the AD

The Application Dictionary allows you to set the OnChange for a specific field, see the OnChange function field in the Window, Tabs and Fields window:

Org.openbravo.client.application.example.onchange ad.png

The value should be the unique global ID mentioned above.

Programmatic registration of OnChange functions

It is also possible register an OnChange function through javascript. This offers more flexibility than defining through the Application Dictionary:

An OnChange function is registered through the OB.OnChangeRegistry.register method. It expects 4 parameters:

An example of a registration:

OB.OnChangeRegistry.register('FF8081813290114F0132901EB0A2001A', 'value',
    OB.OBEXAPP.OnChangeFunctions.Note_Value, 'OBEXAPP_Value');

Multiple OnChange Functions per Field, call order

The OnChange function can have a sort property to control the call-order if there are multiple OnChange functions for one field.

It is for example set like this:

OB.OBEXAPP.OnChangeFunctions.Note_Value.sort = 20;

Some notes on sorting:

Overriding/replacing an OnChange

An OnChange can be registered using an id. If there is already an OnChange with the same id then it is replaced by the new registration.

The OnChange defined through the Application Dictionary has the id 'default'. So by registering a new OnChange using that id you will overwrite the OnChange defined through the Application Dictionary.

Example: OnChange calling a server side action

This section shows an example of an OnChange which calls a server side action:

OB.OBEXAPP.OnChangeFunctions.Note_Value = function(item, view, form, grid) {
  // the callback called after the server side call returns
  var callback = function(response, data, request) {
    form.setItemValue(item, data.upperCased);
    view.messageBar.setMessage(isc.OBMessageBar.TYPE_WARNING, 'Uppercased!', 'The value has been uppercased');
  // do a server side call and on return call the callback'org.openbravo.client.application.examples.OnchangeExampleActionHandler', 
        {value: item.getValue()}, {}, callback);
OB.OBEXAPP.OnChangeFunctions.Note_Value.sort = 20;

The above example calls an ActionHandler class: OnchangeExampleActionHandler. The result is returned and set in a field and a message is shown in the message bar.

It is possible to disable the form during the server side action, call the setDisabled method on the form with the value true as a parameter.

OnChange and the Classic Callout

If a field has both an OnChange and a classic callout defined, then the following applies:

Example Module: example window

The Example Module has an example window with several examples of a callout/onchange function. You can find the example window in Application Examples > Callout/OnChange Function.

Org.openbravo.client.application.example.onchange ex1.png

To test out the onchange, create a new record and set some values in the fields. You should see automatic behavior.

Org.openbravo.client.application.example.onchange ex2.png

You can enable/disable different onchange functions by going into the web/org.openbravo.client.application.examples/js/example-onchange.js file and uncomment some of the commented lines.

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This page has been accessed 12,840 times. This page was last modified on 4 January 2012, at 11:00. Content is available under Creative Commons Attribution-ShareAlike 2.5 Spain License.