[thelist] CF -- have a Q need a Tip to clean-up my webs.

Fri Oct 12 19:54:55 CDT 2001

: I suspect I know... reference vs. value assignment in cfset.
:
: But, I need to _know_.

My experience has been that simple values (the only of which is String in
CF) are assigned by value.  Thus,

<cfset a = "1">
<cfset b = a>
<cfset b = "2">
<cfoutput>#a#, #b#</cfoutput>

yields:

1,2

However, complex variables (Structs, arrays, and queries) are all passed by
reference.  In SP 2 of 4.5.1 (or something like that) they added StructCopy
which does create of copy of the structure.  I know of no such function for
Array and Queries.

Actually, I take that back, I see a function called Duplicate in the help.
It's new to me, but the help file says:

"Returns a clone, also known as a deep copy, of a variable. The copied
variable contains no reference to the original variable."

And goes on:

"This function is very useful in duplicating complex structures, including
nested structures and queries.

Note  You cannot duplicate a COM, CORBA or JAVA object returned from the
CFOBJECT tag or the CreateObject function. If any element in an array or
field of a structure is a COM, CORBA, or JAVA object, you cannot duplicate
the array or structure. If you try to duplicate an object of this sort, an
exception is thrown.  "

<!--- This example shows the use of Duplicate --->
<HTML>
<HEAD>
<TITLE>
Duplicate Example
</TITLE>
</HEAD>

<H3>Duplicate Example</H3>

<CFSET s1=StructNew()>
<CFSET s1.nested  = StructNew()>
<CFSET s1.nested.item = "original">

<CFSET copy=StructCopy(s1)>
<CFSET clone=Duplicate(s1)>

<!--- modify the original --->
<CFSET s1.nested.item = "modified">

<cfoutput>
<P>The copy contains the modified value: #copy.nested.item#</P>
<P>The duplicate contains the original value: #clone.nested.item#</P>
</cfoutput>

</BODY>
</HTML>

HTH,
-joshua