I almost skipped over this post because it was all quotes. ( I imagine that was because the list was bouncing stuff for a bit).
At 08:04 PM 8/31/2002 -0700, you wrote: > > > >> On Friday, August 30, 2002, at 10:35 , Jeffry Houser wrote: > >>> I think this is too good of a topic to pass up, and I haven't seen any > >>> other responses, so.. I'll give it a shot. > >> > >> Well, I was drafting a reply but didn't have time to finish it... and > >> you' > >> ve actually said most of what I was going to say! > >> > >>> There is some parallel to CFCs with Objects, however I think that a > >>> better comparison is Abstract Data Types (ADTs). > >> > >> Interesting comparison. I'm not quite sure why you'd make that > >> comparison given that CFCs map to Java classes directly - could you > >> elaborate? (It's been years since I dealt with ADTs so my recollection > >> of them may be hazy by now) I want to modify my original assertion. There is some parallel to CFCs with classes, however I think that a better comparison is to Abstract Data Types (ADTs). I think everyone understood what I meant, but classes and objects are like comparing apples and oranges, so I wanted to make sure I specified. Before moving on, I will say that a very good argument could be made that CFCs are a hybrid feature encompassing both features of ADTs and Objects. I'll get to more on that later. Moving on: An Abstract Data Type (ADT) is a programmer-defined data type that can be manipulated in a manner similar to system-defined data types. <quote> An ADT must be able: 1. To export a type definition 2. To make available a set of operations that can be used to manipulate instances of the type 3. To protect the data associated with the type so that they can be operated on only by the routines 4. To make multiple instances of the type </quote> To address each issue individually: 1. Do CFCs have an exportable type definition? I would say yes. You can load the CFC in the browser and the component meta data is displayed. That seems to fufill that requirement. 2. Can CFCs make available a set of operations to manipulate instances of itself? Yes! Functions / methods created inside the CFC are by default public and can be used to manipulate component-specific variables. 3. Is the data created inside a component protected from outside forces? I'm a little grey on this one. You can create component specific variables using the this scope. However, I think you can access those variables in the calling page using the componentname.componentvariable syntax, so this is not quite true. 4. Can we make multiple instances of a component? Yep, that is no problem. Just store each instance in a different variable. Common ADTs are Stacks and Queues. I've played around with this concept in both CF5 and CFMX. ( CFCs are better suited for creating Abstract Data Types than anything in CF5 was ). If we can all agree that we have a general understanding of what an ADT is... Objects add new ideas on top of an Abstract Data Type: 1. Object Passing: Any given action happens because a request was made to an object. 2. Overloading / overriding: The same message can mean different things to different objects 3. Inheritance: This means that classes can be developed in a hierarchical manner. One class can have elements / code of its parent. 4. Polymorphism: This is kind of like overloading, except it means that an identical message can do different things in the same object depending on the type of parameter that is being operated upon. Taking each of these elements and placing them on top of CFCs: 1. Do CFCs support object passing? Yes, they do. We can call a method using object notation (I.E. objectinstance.methodname ) However this is really a change in perspective from ADTs. With an ADT we would call a function to place the data on a stack. The emphasis is on the operation. With an object, we tell give the value to the stack and tell it to put the value on the stack. The emphasis is on the data. 2. Do CFCs support Overloading / Overriding? Not in related objects. If two classes have absolutely no correlation, you can do this, however the defeats the purpose of an OO approach. A child CFC inherits all parent methods as is. You do not have the ability to change functionality of inherited methods. 3. Do CFCs support inheritance? Yes, they do. However without the overloading / overriding it is nothing more than a fancy include. 4. Do CFCs support polymorphism? I would say no. I cannot create two different methods with the same exact name, but different argument types. That is the essence of polymorphism. There might be workarounds, though. You could use the cfargument tag with no specified type and then use functions such as IsBoolean and IsNumeric to decide what actions to perform. So, out of four aspects of an Object, ColdFusion supports two of them hands down. For me, the lack of the ability to overload is what makes me say you cannot apply Object Oriented development to ColdFusion and why I say that CFCs are more aligned with ADTS than Objects / Classes. > >> I'd lean toward custom tags for formatting - CFCs should be independent > >> of their environment and should not generate HTML. That approach makes > >> it easier to reuse CFCs later for web services or Flash invocation. That is my thought too. I have no additional comments at this time other than the elaborations / additions to my original E-mail seemed sound. -- Jeffry Houser | mailto:[EMAIL PROTECTED] Need a Web Developer? Contact me! AIM: Reboog711 | Phone: 1-203-379-0773 -- My CFMX Book: <http://www.amazon.com/exec/obidos/ASIN/0072225564/instantcoldfu-20> My Books: http://www.instantcoldfusion.com My Band: http://www.farcryfly.com ______________________________________________________________________ Your ad could be here. 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