How do I pass a variable to a constructor?

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spatz04 - 28 Aug 2007 17:09 GMT

If I have a CFC like the one below:
<cfcomponent>

<cfset init()>
<cffunction name="init" access="public" output="no"
returntype="shoppingCart">
        <cfargument name="cartID" type="UUID" required="yes" >
        <cfset variables.cartID = arguments.cartID>
        <cfreturn this>
    </cffunction>
</cfcomponent>

...how do I pass a requried variable to the constructor? (I am using Flex as
my front end with Flash Remoting to call my CFCs so I won't be instantiating
this from ColdFusion).
Any help appreciated....

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Ian Skinner - 28 Aug 2007 17:18 GMT

> If I have a CFC like the one below:
> <cfcomponent>
[quoted text clipped - 12 lines]
> this from ColdFusion).
> Any help appreciated....

You would have an <mx:method...> in your <mx:RemoteObject...> for the
init function in the CFC. Then you will need to call this from the
appropriate place in your flex application. Maybe in a function called
with the creationComplete event.

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spatz04 - 29 Aug 2007 09:01 GMT

Say for example I have the following CFC called test.cfc:

<cfcomponent>
<cfset init()>
<cffunction name="init" access="public" output="no" returntype="test">
        <cfargument name="cartID" type="numeric" required="yes" >
        <cfset variables.cartID = arguments.cartID>
        <cfreturn this>
    </cffunction>
</cfcomponent>

...and I have the following CFM file that calls it.....test.cfm.....

<cfobject component="test" name="comp">
<cfset comp.init(6)>
<cfdump var="#comp.init(6)#">

This will cause an error saying the parameter cartID to function init() was
required but not passed in, because the constructor call ( <cfset init()> )
does not pass a parameter to the init function. The only way I can get this to
work is to comment out the <cfset init()> line. I guess I don't need this in
my scenario because I'm calling the init method directly anyway.

FYI: I've been following Ben Fortas phone selector example ( a good example of
building a simple Flex/CF app):
http://www.adobe.com/devnet/flex/articles/coldfusionflex_part3_02.html

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Ian Skinner - 29 Aug 2007 15:46 GMT

Yes you would not use the <cfset init()> line in the pseudo constructor.
Then, as you where doing in your cfml example, you will call init()
directly in your code.

Then to translate this to your mxml, you would put a <mx:method
name="init" ...> tag in your <mx:remoteObject... tag block. Then as
some relevant part of your code you would call the init() method in your
mxml. Very likely on some creationComplete() event.

One thing to remember, without using more sophisticated techniques, a
CFC can not maintain state when using remote calls. This is true for
flex|flash remoting or web services. In other words you can't make one
call to a method to set a value, then make another call to return the
value when using remote methods.

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Webmaster Forum / ColdFusion / Advanced Techniques / August 2007

How do I pass a variable to a constructor?