Ben Forta uses both cfinvoke and cfobject in his tutorial at
http://www.macromedia.com/
Livedocs says
"When the cfobject tag creates an instance of the CFC, ColdFusion executes any constructor code in the CFC; that is, it runs code that is not in the method definitions."
I'm not sure I know what an example of constructor code would be.
It also says
"Separate instantiation and method invocation; permits multiple invocations."
http://livedocs.macromedia
I KNOW I don't know what that means! I think it just means they're using it twice in their example.
From what I can tell, cfinvoke uses named arguments and cfobject passes arguments by location.
Here's an example passing two arguments using cfobject:
<CFOBJECT NAME="usrObj" COMPONENT="CFComponent">
<cfoutput>#usrObj.GetEMail
And here's a example of using cfinvoke with named arguments:
<cfset args = StructNew()>
<cfset args.UserID = "psenn">
<cfset args.Password = "test">
<CFINVOKE COMPONENT="CFComponent"
METHOD="GetEMail"
argumentCollection="#args#
RETURNVARIABLE="X">
<cfoutput>#X#</cfoutput>
Various authors have recommended using name value pairs when passing arguments, so that's one vote in favor of using cfinvoke.
Q: Which do you prefer? CFINVOKE or CFOBJECT.
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Well, constructor code is any code that is not found within the functions of the Coldfusion Component. Usually, this type of code is used to display output without invoking any functions:
<cfcomponent>
<cffunction name='test'>
...
</cffunction>
<cfoutput>
Hello World!
</cfoutput>
</cfcomponent>
Basically, the Hello World! text within the <cfoutput> tags would be your constructor code. So, what I think the LiveDocs are trying to imply, is that as soon as the Coldfusion Component is initiated using the <cfobject> or createobject() tag, the code in the .cfc that is not within a function is executed.
But that is not the case with <cfinvoke>, because with <cfinvoke> you are not initiating the entire component first, instead you are initiating 1 function within the component and then closing the component.
So if you were to invoke 2 functions of a Coldfusion Component using <cfinvoke>, you would then be opening 2 connections to the Component, but with createobject() and <cfobject>, you are opening the entire component for the page request, and you can then call any functions of that component in dot notation.
Ofcoarse you can, I use it all the time to return queries in my application. Basically this would be your component, let's name this component "data.cfc":
<cfcomponent>
<cffunction name='getquery'>
<cfquery name='qname' datasource='datasource'>
...
</cfquery>
<cfreturn qname>
</cffunction>
</cfcomponent>
That would be your Coldfusion Component which would run a query in the getquery() function and return the query in <cfreturn>. Now this would be your .cfm file that calls the function of the Component and displays the query results:
<cfobject name='queryrecords' component='data'>
<cfset showquery = queryrecords.getquery()>
<cfdump var='#showquery#'>
And there you go. First you use <cfobject> to initiate the Component, then you call a function of the component within the <cfset> tag, and set the return query to "showquery" variable, within the same <cfset> tag.
"constructor code" is the code that gets executed every time you create a new instance of an object. for example, if you have a class that is defined like:
begin class
x=1
y=2
add(x,y)
{
return x+y
}
setx(a) { x=a }
sety(a) { y=a }
subtract(x,y) { return x-y }
end class
then the constructor code would be that which sets the initial values of x and y, each time you set up a new object of this class.
hope that helps explain it a little.
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by: andw928Posted on 2005-08-16 at 21:41:10ID: 14689088
It basically comes down to this, if you have multiple functions in a Coldfusion Component that you want to use on the same page request, then use <cfobject> or createobject(), otherwise, if you only have 1 function in the Coldfusion component or want to use only 1 function on a certain page request, then use <cfinvoke>.
There is a reason for this, when you have more than 1 function that you are invoking from a Coldfusion Component using <cfinvoke>, you are then really invoking the component twice for each of those functions. While, if you are using createobject() of <cfobject>, then you are invoking the component first, but leaving it open, therefore allowing you to call the functions of the component on that page request without closing and opening the component each time you call the function.
So by multiple innvocations, it means exactly what I just explained. So basically ask yourself this question:
Do I want to use more than 1 function from the .cfc on the current page?
-If yes, use <cfobject> or createobject().
-If no, use <cfinvoke>.