Re: [CFCDev] Copying a CFC instance?!

Matt Liotta Mon, 05 Apr 2004 10:38:12 -0700

The practice of using a struct to store instance data certainly makes a lot of sense when you want to implement a clone method since the duplicate function works correctly on a struct. I would certainly advocate that approach and additionally, I would suggest Nathan add this information to his document.

-Matt

On Apr 5, 2004, at 12:34 PM, Nathan Dintenfass wrote:

There's no built-in way to do it.

It's fairly easy to build a clone() method that creates a new instance of the same CFC and then copies the instance data over. As an aside, this is one of the reasons I like to create a sub-struct inside of the VARIABLES scope for my private instance data -- so it can be copied as a single unit to a cloned instance.

So, for instance, you might have "package" methods that look like:
getInstanceData();
setInstanceData(struct);
hasInstanceData();
If you had a "virtual scope" in your Variables scope called "instance",
these might look like:
<cffunction name="getInstanceData"
                        access="private"
                        output="no"
                        returnType="struct"
                        hint="returns the instance data of this component">
        <cfreturn duplicate(instance)>
</cffunction>
<cffunction name="setInstanceData"  access="package" output="no" returnType="void" hint="Given a structure, overwrites any existing instance data with that"> <cfargument name="data" type="struct" required="yes"> <cfset structAppend(instance,arguments.data,true)> </cffunction>
<cffunction name="hasInstanceData"
                        access="private"
                        output="no"
                        returnType="boolean"
                        hint="Tells whether the current component has instance data">
        <cfreturn isDefined("instance")>
</cffunction>
You can then make a public method called clone() that might look like:

<cffunction name="clone" access="public" output="no" returnType="yourComponentType" hint="makes a clone of this component">  <cfset var anInstance = createObject("component","yourComponentType")>  <cfif hasInstanceData()> <cfset anInstance.setInstanceData(getInstanceData())> </cfif> <cfreturn anInstance> </cffunction>

The only complication will be if you end up with other CFCs/Objects in your instance variables, since the duplicate(instance) line in getInstanceData will fail. In that case you'd need to somehow determine which CFCs/Objects they were and have a way to clone each of them.

I also once built a general purpose duplicateCFC() UDF, but it doesn't take into account the scenario of CFCs as instance variables (and had some other issue I can't remember now), but it might help you:
<cfscript>
function duplicateCFC(instance){
        var newInstance = "";
        var error = "";
        var templateProxyFactory = "";
        var fileObject = "";
        var instanceData = "";
        var key = "";
        //if THIS is defined, we must be attached to a CFC, so act that way
        if(isDefined("this")){
                //if the argument is a struct, set the variables in this instance
                if(isStruct(arguments.instance))
                        structAppend(Variables,arguments.instance);
                //otherwise, just return Variables to get them out of this instance
                else
                        return Variables;
        }
        //if THIS is not defined, we are being called on the instance
        else{
                //take the method onto the instance
arguments.instance.temporaryMethodNameThatNobodyWillEverUseBecauseItRun sDupl icateCFC = duplicateCFC; //first, try making it with the "path", because that's fastest try{ newInstance = createObject("component",getMetaData(arguments.instance).name); } //if something goes wrong, try making the instance based on the absolute file path catch("Application" error){ templateProxyFactory = createObject("java","coldfusion.runtime.TemplateProxyFactory"); fileObject = createObject("java","java.io.File"); fileObject.init(getMetaData(arguments.instance).path); newInstance = templateProxyFactory.resolveFile(getPageContext(), fileObject); } //now, we attach this method to the new instance as a temporary method name

newInstance.temporaryMethodNameThatNobodyWillEverUseBecauseItRunsDuplic ateCF C = duplicateCFC; //grab the instance data from the original //THIS SHOULD POSSIBLY DO A DEEP INSPECTION TO ACCOUNT FOR OBJECT INSTANCES INSIDE THE VARIABLES OF THE INSTANCE instanceData = duplicate(arguments.instance.temporaryMethodNameThatNobodyWillEverUseBe cause ItRunsDuplicateCFC("")); //clean off the instanceData -- delete THIS structDelete(instanceData,"this"); //loop through the rest and grab everything that's not a function for(key in instanceData){ if(isCustomFunction(instanceData[key])) structDelete(instanceData,key); } //put the the variables from one into the other

newInstance.temporaryMethodNameThatNobodyWillEverUseBecauseItRunsDuplic ateCF C(instanceData); //now kill the temporary methods from the component instances

structDelete(arguments.instance,"temporaryMethodNameThatNobodyWillEverU seBec auseItRunsDuplicateCFC");

structDelete(newInstance,"temporaryMethodNameThatNobodyWillEverUseBecau seItR unsDuplicateCFC"); return newInstance; } } </cfscript>
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Alexander Sherwood
Sent: Monday, April 05, 2004 8:56 AM
To: [EMAIL PROTECTED]
Subject: [CFCDev] Copying a CFC instance?!
Please help:
Just realized that using Duplicate() on an instance of a CFC
returns a bare struct. Apart from creating a new object, is there
a way to copy create an instance of a CFC from an existing
instance (that copied by value, no by reference)?
Any help would be massively appreciated.

Thanks!
----------------------------------
Alex Sherwood
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Re: [CFCDev] Copying a CFC instance?!

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