Second, we have observed that static data is rarely used in other classes except as private data within the class or as public constants. For example, a survey of several Java class libraries found that all public static fields were also final. In MATLAB, Constant properties can be used like “public final static” fields in Java. For data internal to a class, MATLAB already has persistent variables that can be created inside of private or protected methods or local functions privately used by a class. There are also good reasons to avoid static data in MATLAB where possible. If a class has static data, it can be difficult to use the same class in multiple applications because the static data can be a source of conflicts among applications. In some other languages, this is less of an issue because different applications are separately compiled into executables running in different processes with different copies of class static data. In MATLAB, frequently many different applications may be running in the same process and environment with a single copy of each class.

—————————
classdef myClass
properties (Static)
x = 1 ;
end
methods (Static)
function f(val)
myClass.x = val ;
end
end
end
—————————

and the get method works:

—————————
> myClass.x
ans = 1
—————————

but the set method does not work, either on the command-line or via a static method function!

Thanks,
Lee

I haven’t figured out how to make a class property that can be modified/assigned. Using the “Constant” attribute on a property, like you mentioned, makes the value unchangeable.

As an example:

classdef myclass
properties (Constant, SetAccess=public)
prop=1; % initial value
end
methods
function set1(obj,val)
obj.prop=val;
end
end
methods (Static,Access=public)
function set2(val)
myclass.prop=val;
end
end
end

… and then I try to use use the class to modify my property:

>> myclass
ans =
myclass
properties:
prop: 1
list of methods
>> myclass.set2(10)
>> myclass
ans =
myclass
properties:
prop: 1
list of methods
>> obj=myclass()
obj =
myclass
properties:
prop: 1
list of methods
>> obj.set1(10)
??? Setting the ‘prop’ property of the ‘myclass’ class is not allowed.

Error in ==> myclass>myclass.set1 at 7
obj.prop=val;

None of my attempts have been successful. This behavior is consistent with my idea of a constant (never ever changing). Yet, in the documentation under the heading “Defining Named Constants,” it says, “Note that setting the Constant attribute to true effectively sets the SetAccess to private, so that the values of the properties cannot be changed outside of the class.” That implies that one should be able to change the value of a constant from within a class’s method as I tried, and it also implies a conflict with my combination of “Constant” and “SetAccess=public” above.

Is there a way to modify my example to implement a class property whose value is publicly changeable (i.e. myclass.prop=10), yet uniform across all instances of the class?

Both class and class instance(object) properties can be scoped by the public/protected/private qualifier. Static properties are associated with a class and are declared public to access them outside the class. So, I am not sure why you say that public/protected/private options are not implemented for class properties. Could you clarify?

The ambiguity in property names isn’t unique to static properties. Mistakes with typos could be avoided with the help of an affordance like tab-completion for properties which we are looking to provide in the future.

OOP in MATLAB isn’t modeled after any particular language but several languages including Java, C++, and C# have had an impact on its design. We will continue to evolve our offering in this area.

Nausheen

Thanks for the correction. That helps! I must have attempted to modify my constant property with an object method when I tried. Is there a particular reason that public static variables are not allowed? Obviously they can be controlled from outside a class using static get and set methods, but it seems peculiar that public/private/protected options would be implemented for object properites and not class properties. In playing with 2008a, it does seem like there would be some tricky ambiguities or hard-to-find errors if a user could assign a public static class property (e.g. classname.propname=10;), and instead, due to a type-o (e.g. classnam.propname=10;), got a new struct in the workspace named “classnam.”

Is the direction of MATLAB’s new OOP features modeled after any existing languages (e.g. Java, C#, Python)? Should users expect additions to the OOP feature set in future releases?

You can define static properties by setting the Constant attribute for properties to true. The values can only be changed by a static method of the class with static properties.

Hope this helps.
Nausheen

I just got a trial of 2008a, so I’ve only gotten my feet wet. Meta-classes, abstract declarations, dynamic properties, and the dot-sytnax for calling methods (e.g. obj.method(var) instead of method(obj,var)) are all great features for making tools that are easy to use and maintain. The ability to declare static methods for a class is a godsend.

The first glaring omission I see is static properties. Why weren’t they included with the new OOP? Am I missing something?

-Arthur

You can find out information about platform support here .

–Loren

The above results are then obtained…