Properties

As a new feature, CoolBasic V3 will support class properties. You may have already seen a hint for property support when I discussed about the String implementation earlier in this blog. Properties work just like any other Public variable, i.e you can access then by using the dot notation, but with a added twist. Normally, when you either assign or read a value from a Public variable nothing else will happen. But with properties you are able to capture this event, and execute your custom code to get the job done. Basically, we’re talking about old-fashioned way of creating getter and setter -functions. Without properties you’d have to write these two functions in order to access, say Private variables:

MyClass.SetName("hello")
Console.WriteLine(MyClass.GetName())

With properties you could do the same in more decent way:

MyClass.Name = "hello"
Console.WriteLine(MyClass.Name)

You still define the getting and setting code within the property structure, but done so they’re unaccessible from outside. So you have nice little black box of which workings not even the class members know about. There’s a difference in using the property name than assigning the value to the private variable in question by hand – even when all the setter does is the assign. There’s always code involved when accessing property values.

In addition you can define the property as ReadOnly or WriteOnly. By doing this, you protect some data that must not be modifier from outside. One example of a ReadOnly property would be the length of a string. The property returns the value of a Private variable, however this information is related to the actual data within the String class, and should only be updated when this inner data changes. It’s the only way of keeping such information in sync in a secure way. Now if you come to think about it, constants are ReadOnly, too (except that CoolBasic compiler doesn’t work like .NET compilers in this regard).

Since properties are really a set of methods, they can be inherited. This also means that things like overriding, are possible. However, at this point in time, I’m still a bit unsure about one thing called Default property. A property can be defined as Default when you access the object without providing further dot notation. Sound like normal object reference? Well, there’s a catch. In VB.NET Default properties always need atleast one parameter which means you must include a set of brackets to it. A typical example would be the myVar.Item(index) property you could refer to just myVar(index). I don’t like this because it’s easy to mix this to a method call.

On the other hand, I would still have to allow parameters for properties because it’s the only way to implement indexes to them. Like above. If I ever wanted to implement LinkedLists or Lists or any variant, I, in fact, must allow this. There are still lots of questions floating I need to chew on.