On Fri, 24 Dec 2004 19:19:29 -0600, Jared Rypka-Hauer - CMG, LLC
<[EMAIL PROTECTED]> wrote:
> Perhaps I should begin my question with my perhaps-incorrect
> understanding of instances. I have always understood an "instance" to
> be a unique, individual memory-resident copy of an object that
> contains methods and properties, or functions and attributes, or
> whatever they be called in your current universe. An "instance" of an
> "object" would, then, be the result of a call to the object's codebase
> from within an existing thread, and it's constructor would fire as
> soon as the CFOBJECT or createObject executed.
Yup, that's pretty close although CFCs don't really have constructors.
When you create an instance, CF will execute the "pseudo-constructor",
the code that is inside <cfcomponent> but outside of any <cffunction>
tag.
A lot of people have adopted the practice of defining a method called
"init" to act as the constructor (so that the same syntax that calls a
Java object's constructor with arguments can be used for CFCs).
<!--- constructor for MyObject.cfc --->
<cffunction name="init" returntype="MyObject" access="public" output="false">
... arguments ...
... initialize the instance ...
<cfreturn this />
</cffunction>
Then you can construct and initialize in one statement:
<cfset obj = createObject("component","MyObject").init(args) />
(change "component" to "java" and the same syntax will work for MyObject.java)
> I've always assumed that an instance would be intrinsically
> thread-safe if the underlying engine was also thread-safe.
It depends where you store the instance. If you store the instance in
a per-request variable, it'll be thread-safe. If you store it in a
shared scope, it'll be subject to the same issues as any other shared
scope variable (assuming the instance stores state information in
"this" scope or "variables" scope).
> And, in that case, it's
> THIS scope would be available to all methods within the instance
And to everything outside the object. "this" scope is public,
"variables" scope is protected (in Java-speak).
> whatever non-scoped var you create within a method would be
> function-local by default?
Function-local requires use of the "var" keyword:
<cfset var x = "I'm local" />
<cfset y = "I'm in 'variables' scope - protected instance data" />
"var" is used at the top of the function to declare a function-local
variable. The second statement (the assignment to "y") is equivalent
to:
<cfset variables.y = "I'm in 'variables' scope - protected instance data" />
> Until now, I've been using this THIS scope A LOT, not VARing any of my
> method variables, and wrapping CFLOCKS around calls to methods that
> would alter the data within a session-scope persistent CFC. Have I
> been doing this wrong?
Yes. Probably. Using "this" scope is definitely 'wrong' because it's
public data. If you want variables that are function-local, you need
to declare them with "var". If you want instance data shared between
multiple method calls, you should use "variables" scope.
> So, now that I've laid my ignorance out for you all to see, please be gentle?
> :D
Hope my comments help?
--
Sean A Corfield -- http://www.corfield.org/
Team Fusebox -- http://www.fusebox.org/
Breeze Me! -- http://www.corfield.org/breezeme
Got Gmail? -- I have 6 invites to give away!
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
Special thanks to the CF Community Suite Gold Sponsor - CFHosting.net
http://www.cfhosting.net
Message: http://www.houseoffusion.com/lists.cfm/link=i:4:188773
Archives: http://www.houseoffusion.com/cf_lists/threads.cfm/4
Subscription: http://www.houseoffusion.com/lists.cfm/link=s:4
Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4
Donations & Support: http://www.houseoffusion.com/tiny.cfm/54
