Interesting article.
Encapsulation is the result of a process of discrimination. It is a
declaration of something that is by discarding anything it is not. The
article mentions defining the rules this illustrates discrimination. "Data
hiding is indeed encapsulation" is true but encapsulation is data hiding is
not true. Encapsulation is far more.
Private variables is data hiding is encapsulation dismisses public
variables is class is encapsulation. Encapsulation is class is fact and
behavior. Fact is variables of type public or private. Behavior is methods.
ISA statements are not exclusive and not a converse axiom. The statement
"encapsulation is data hiding" is a red herring. Whereas, "data hiding is
encapsulation" is mostly correct because it is not exclusive.
Back to the original question about using this scope variables in CF. The
very fact that a CFC is defined, is a discrimination of all other facts and
behaviors. Whether or not the discrimination is complete in the problem
domain is another consideration. The use of pubic variables does not
violate encapsulation, it only violates some opinions on how to implement
encapsulation.
If using public variables satisfy the problem domain, most likely using
them will be productive.
- - Part of the reason I published CFSQLTool under GNU was as comprehensive
study on using public variables in data access layers. The table wrapper
code wizards generate not only database queries but also form queries using
the same public variables. Form queries and database queries can exist
within the same class as a data access layer.
At 07:03 AM 8/31/2005, you wrote:
Data hiding is indeed encapsulation. There are may types of
encapsulation: data hiding, implementation, object creation, and
system design. NetObjectives has a very nice article on using
different types of encapsulation to identify patterns:
http://www.netobjectives.com/ezines/ez0508NetObj_IDPatternsTermsEncap.pdf
And just a note that you if you don't want to have to write getters
and setters for every property, you can still make the variables
private rather than public by creating a single get method that gets
any property: getProperty( 'firstName' ). This way you only have one
method, but external code can only change the properties if you allow
them to (by going through a setter).
Regards,
Brian
On 8/31/05, Joseph Flanigan <[EMAIL PROTECTED]> wrote:
> THIS scope variables simply mean the variable is a public memory structure.
> Every CFC has a public memory structure. For the most part, these are
> either functions or variables spaces that can be accessed by a calling
> application.
>
> A CFC itself defines an encapsulated memory structure. Its definition is a
> potential instance of an object. Encapsulation is a design decision. Data
> hiding is not encapsulation. The common technique for implementing data
> hiding is using getter and setter functions to access private
> variables. Getter and setters can be used to very effectively on public
> variables just as well as private variables. (See table wrapper CFC
> generated by CFSQLtool for practical examples.)
>
> If an application has overloaded use of a CFC for data type changes, getter
> and setter are worth considering. Some examples of OO overstate
> encapsulation to include data hiding. Which is fine as long as the meaning
> is obvious. Data hiding may be useful when functions are overloaded.
>
> Public variables are practical. For me, CFC public variables are very
> productive. Once a memory structure is instanced as an object, it's
> structure is well defined. Instances of public variables are easy to
> reference by simple assignment whereas to reference private variables
> requires get and set functions.
>
> Some descriptions of "encapsulation" may better described as overloading.
> For example, a function that calculates price of gas can be overloaded with
> volume types of either gallons or liters.
>
>
>
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