Detecting default values

So I haven’t posted in a long time. I finally fixed some technical issues on the blog and upgraded to a recent version of WordPress. Let’s start with a quick tip to warm up 🙂

As you know X++ supports methods with default values. In Ax it’s possible to detect when such a default value was used at runtime with prmIsDefault(). To see this for yourself, create a class with a method like this:

void someMethod(int i = 1)
{
    ;
 
    if (prmIsDefault(i))
    {
        info('Default');
    }
    else
    {
        info('Value given');
    }
}

And call it from another method.

    o.someMethod();
    o.someMethod(1);

Even though the value is the same in both cases a different info message will be displayed.

Now you may be wondering how this can be useful. Some scenarios:

• Avoiding expensive operations if the default value was used
• Avoiding unwanted initializations
• Dealing with customizations that require extra parameters in standard Ax classes

If you do a search for prmIsDefault() in the AOT you will see it’s used often. Classes with the Ax prefix are the most obvious example. Because getters and setters are rolled into a single method it’s necessary to know if the method was used as a getter or a setter and keep track of modified fields.