Passing A Variable Number Of "Nameless" Arguments Using CFInvoke And ArgumentCollection
Posted March 30, 2007 at 8:39 AM
I have been trying to figure out how to send a variable, logic-based selection of arguments as unnamed values to a function. My original thought was to use ColdFusion's CFInvoke and CFInvokeArgument, but CFInvokeArgument requires a name attribute (which is what I was trying to avoid). I couldn't just call the function using function notation (ex. "Test()") as I needed to involve logic in my argument selection (which only CFInvoke would allow).
Sean Corfield had a good idea to use the index-like keys. But for some reason, it didn't click in my head until Christoph Schmitz suggested the same thing. While both suggested this solution, I think it only dawned on me "how" to accomplish this when Chris said it (right place, right time). Both are clearly rock stars though.
So anyway, here is my test to see that it works. These are two functions that I tested with. The first, DumpArgs() is the ColdFusion UDF that just dumps out its arguments. The second function, StructCreate() is just a utility function (seen all over the place) that builds a struct on the fly and returns it:
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- <cffunction
- name="DumpArgs"
- access="public"
- returntype="void"
- output="true"
- hint="Does nothing but CFDump out the arguments.">
-
- <!--- Dump out arguments. --->
- <cfdump
- var="#ARGUMENTS#"
- label="ARGUMENTS Scope"
- />
-
- <!--- Return out. --->
- <cfreturn />
- </cffunction>
-
-
- <cffunction
- name="StructCreate"
- access="public"
- returntype="struct"
- output="false"
- hint="Returns a created struct based on the passed in key-value pairs.">
-
- <!--- Define the local scope. --->
- <cfset var LOCAL = StructNew() />
-
- <!--- Create the return struct. --->
- <cfset LOCAL.Struct = StructNew() />
-
- <!---
- Populate the struct using the name-value pairs
- of passed in arguments.
- --->
- <cfloop
- item="LOCAL.Key"
- collection="#ARGUMENTS#">
-
- <cfset LOCAL.Struct[ LOCAL.Key ] = ARGUMENTS[ LOCAL.Key ] />
- </cfloop>
-
- <!--- Return struct. --->
- <cfreturn LOCAL.Struct />
- </cffunction>
Ok, now I need to create some values that I may OR may not need to pass in. It's friday, let's build a struct of hot girls that we can choose from:
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- <!--- Create a struct of girls. --->
- <cfset objGirls = StructNew() />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Samantha" ] = StructCreate(
- Name = "Samantha",
- Hair = "Brunette",
- Hotness = 9.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Niki" ] = StructCreate(
- Name = "Niki",
- Hair = "Brunette",
- Hotness = 8.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Lori" ] = StructCreate(
- Name = "Lori",
- Hair = "Blonde",
- Hotness = 7.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Tamoko" ] = StructCreate(
- Name = "Tamoko",
- Hair = "Black",
- Hotness = 8.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Ashley" ] = StructCreate(
- Name = "Ashley",
- Hair = "Brunette",
- Hotness = 8.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Libby" ] = StructCreate(
- Name = "Libby",
- Hair = "Brunette",
- Hotness = 9.0
- ) />
-
- <!--- Create girl. --->
- <cfset objGirls[ "Christina" ] = StructCreate(
- Name = "Christina",
- Hair = "Blonde",
- Hotness = 9.0
- ) />
Now that we have a our function in place and our possible values, let's create a variable-length argument collection based on some business logic:
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- <!---
- Create an argument collection of girls. The
- purpose of this is to build up a variable number
- of "nameless" arguments.
- --->
- <cfset objArgs = StructNew() />
-
- <!---
- Loop over the girls to figure out which ones we
- want to pass in. For now, let's get all the 9.0
- who are also brunette.
- --->
- <cfloop
- item="strGirl"
- collection="#objGirls#">
-
- <!--- Get a reference to the girl. --->
- <cfset objGirl = objGirls[ strGirl ] />
-
- <!--- Check to see if this girl makes the cut. --->
- <cfif (
- (objGirl.Hair EQ "Brunette") AND
- (objGirl.Hotness EQ 9.0)
- )>
-
- <!---
- We want to include this girl in our argument
- collection. In order to do that we are going to
- add her to the argument collection struct with an
- index-based naming convention so that the function
- will use it like an array. In order to do this
- dynamically, we can use the struct-count to get
- the current index.
- --->
- <cfset objArgs[ StructCount( objArgs ) + 1 ] = objGirl />
-
- </cfif>
-
- </cfloop>
-
-
- <!---
- Now that we have built up the argument
- collection, we can simply invoke the method and pass
- in the arguments struct.
- --->
- <cfinvoke
- method="DumpArgs"
- argumentcollection="#objArgs#"
- />
This gives us the following CFDump:
| | | | ||
| |  | | ||
| | | |
That works perfectly! I think the thing that finally clicked in my head when Chris suggested the argumentCollection was how to build the struct without having to use an incrementing value (ie. keeping some sort of argument count variable). By using the StructCount() I was able to just keep appending values to the struct and not having to worry about what index I was actually working on. Sweet!
Note: Using argumentCollection can also be done with standard function invokation. It does not require the use of CFInvoke.
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Reader Comments
Ben, take a look at my experimental CFC framework. This is exactly how i pass data between different methods. There are a few different viewlets demonstrating how it all works.
http://labs.webapper.net/projects/CFCFramework/index.cfm
FWIW, #dumpargs(argumentcollection=objArgs)# would work just as well as <cfinvoke method="DumpArgs" argumentcollection="#objArgs#" />
@Steve,
The PPT looks cool. I will take try to take a look at the other files this weekend.
@Matt,
Yeah, good point. I was just using CFInvoke cause that's how I started out. But you are absolutely right.
@Steve,
I finally got around to going through your CFC framework. It looks pretty interesting. I see what you are saying about passing around all of your arguments like this; you are continually passing your ARGUMENTS scope onto other methods.
I don't know enough MVC / Fusebox to comment on the functionality, but it does look very clean. I am sure it will positively influence my future thought processes.
