Extending a Form Data Source Method Using Chain of Command in D365 F&O - X++ Code

Extension of a form data source method - D365 F&O - X++ Code

Chain of command is an option that helps you enhance the functionality of a form data source method. This option is applicable for standard methods and custom methods of the form.

You can use the following code pattern if you need to extend the initValue() method of the form data source:

[ExtensionOf(FormDataSourceStr(Currency, Currency))]
final class CurrencyFormCurrencyTableDataSource_Extension
{
    public void initValue()
    {
        //code
        next initValue();
        //code
    }
}

In X++, the ExtensionOf keyword is used to create a class extension that extends the functionality of an existing class. In this case, the CurrencyFormCurrencyTableDataSource_Extension class extends the Currency table data source class, as specified by the FormDataSourceStr(Currency, Currency) function call.

The initValue() method is a built-in X++ method that is called when the data source is initialized. The next initValue() statement in the initValue() method is used to call the initValue() method of the parent class, which in this case is the Currency table data source class.

By using next initValue() to call the parent class's initValue() method, any initialization code in the parent class is executed before the initialization code in the CurrencyFormCurrencyTableDataSource_Extension class. This ensures that any necessary initialization tasks are completed before the extension's code is executed.

Here's an example of how you might use ExtensionOf and next initValue() to extend the functionality of the Currency table data source class:

[ExtensionOf(FormDataSourceStr(Currency, Currency))]
final class CurrencyFormCurrencyTableDataSource_Extension
{
    public void initValue()
    {
        // Call the parent class's initValue() method first
        next initValue();

        // Add custom initialization code here
        info("Currency table data source has been initialized.");
    }
}

In this example, we define the CurrencyFormCurrencyTableDataSource_Extension class as an extension of the Currency table data source class. In the initValue() method, we call the parent class's initValue() method using next initValue(), and then we add our own custom initialization code, which simply displays an information message.

By using class extensions and the next initValue() statement, we can easily extend the functionality of existing X++ classes, while still ensuring that any necessary initialization tasks are completed correctly.