dougrdotnet

Today a question came up regarding the difference between constant fields and static fields and I thought it noteworthy to mention here as it is easy to casually use static when one’s intention is really to define a constant.  Prior to AS 3.0, const was not available.

In short, a field declared as static const is indeed read-only, however, if declared as static it may be writable from inside or outside of its containing class, depending upon its access modifier (see Basic Modifiers below), and there is not a requirement for an instance of that class to be created in order for it to be referenced. Fields declared as constants may not be modified, they are constant.

It is interesting to note that a static field declared in a class may have the same name as an instance variable – the rule is that while both vars of the same name may be used in the instance, the static variable must be preceded by the classname (i.e. MyClass.variableName), whereas the instance variable would simply be declared by name.

Basic Modifiers:
Internal: the default if no modifier is specified – allows internal and package level access
Private: provides the greatest degree of access restriction – allows only internal access
Public: provides the least degree of access restriction – its an all-access pass
Protected: provides package level access restriction – allows internal and subclass access