When and when not to use hash # symbol in ColdFusion?

Question

I use the # symbol around every dynamic value in my application and after posting some of my code on here for help, I've been told there's no need to use the # in many places e.g. <cfif> statements.

So I have started removing the # symbols, until I realised I broke my application because I removed the # symbols from the value="" attribute of a <cfprocparam> tag.

I am confused as to:

1. Why use the # symbol is some places and not others (and what is the benefit of not using it?)
2. Why if they are not required in <cfif> and <cfargument> tags are they suddenly required in <cfprocparam> tags?
3. Due to this lack of consistency, is it not better to just wrap hashes around every dynamic value in the first place?

Answer 1

There is no inconsistency (or very little: none of what you cite are inconsistencies), it's just you not understanding the rules (which are pretty basic really). It's all in the docs: "Using number signs"

In short, within a CFML statement, all elements are considered CFML, so there is no need to specifically mark them as such. EG:

<cfset myVar = someFunction(anArgument)>

There is no ambiguity there that myVar, someFunction and anArgument are anything other than CFML constructs, so no need to do this sort of thing:

<cfset myVar = #someFunction(anArgument)#>

As some people are inclined to do.

In the middle of text or within a string, there is ambiguity as to what's text and what's CFML, so one needs to use pound signs to mark them as such. EG:

<cfset myVar = "The time is #now()#">

It's necessary to us pound-signs there to disambiguate now() as being a CFML statement, an not just part of the string, eg:

<cfset myVar = "CFML has a function now() which returns the current timestamp">

Equally:

<cfquery>
    SELECT col1
    FROM table2
    WHERE col2 = #someValue#
</cfquery>

There would be no way of knowing someValue is a variable there without marking it as such.

That's basically it. It's not complicated.

Answer 2

Rule 1: If you are inside of quotes, then you are pushing a string. If you want a substitution, the you use #name#

Rule 2: If you are inside of a <cfoutput>, you are generating a string.

While it is possible to write

<cfif "#name#" EQ "bob">Hi Bob</cfif>

It is easier to write

<cfif name EQ "bob">Hi Bob</cfif>

Rule 3: I think that <cfoutput query="qryData"> is kinda wrong, I have written it so much, I don't think much of it.