If you find yourself needing to trigger an independent display method within a form class upon the occurrence of a variable change, data source modification or event, employing the X++ observer can be of help.
There are three distinct methods to utilize the X++ observer:
One approach is to employ the observe() method of a datasource object. With this method, whenever a change occurs within a datasource, any associated code encompassing the <datasource>.observe() call will be executed.
//Example 1 – FormDataSource observe
[ExtensionOf(formStr(SimpleForm))]
final class SimpleForm_Form_Extension
{
public display boolean displayCallMyMethodByFormDataSourceObserver()
{
myFormDataSource_ds.observe(); //Called FormDataSource observer()
return isThisHelpful();
}
}You can define a variable with the [FormObservable] attribute. Whenever this variable undergoes a change, the corresponding code that utilizes it will be executed.
//Example 2 – FormObservable attribute
[ExtensionOf(formStr(SimpleForm))]
final class SimpleForm_Form_Extension
{
[FormObservable]
private int counter;
public void someMethod();
{
//Code ...
counter = 0; //<--- Changing variable with FormObservable attribute
//Code ...
}
public display int displayCounter()
{
return counter; //Called because of FormObservable attribute
}
}Another option is to utilize the FormObservableLink class for creating a FormObservableLink object. With the markChanged() method, you can initiate a change, and by employing observe(), you can capture the change event.
//Example 3 – FormObservableLink calls
[ExtensionOf(formStr(SimpleForm))]
final class SimpleForm_Form_Extension
{
private int counter = 0;
FormObservableLink fOL = new FormObservableLink(); //1. Create a instance of FormObservableLink
public void someMethod();
{
//Code ...
counter = 0;
fOL.markChanged(); //2. Call change somwhere
//Code ...
}
public display int displayCounter()
{
fOL.observe(); //3. Called through markChanged();
return counter;
}
}May this aid you in your continued journey within the realm of Microsoft D365 F&O development.
Another useful posts about this topic:
Blog on Microsoft Dynamics AX/ D365: Observer x++ D365FO (sangeethwiki.blogspot.com)
FormObservableLink works in data source extensions – Goshoom.NET Dev Blog