CFCs and OO design

[g1zm0guy]

Howdy folks,

I am new to using CFC's (and to be honest, new to OO in general), and I'm
trying to use them for the first time. Let me explain my problem:

I'm writing a program to staff a temp employee for a specific shift on a
specific date. Requirements are that the employee must be able to work on that
day, must be active in the database, have the appropriate skill set, be willing
to work in the appropriate region, etc.. I then populate a dropdown list with
all the employees who match the criteria so the user can choose whom to staff.

In the past, I've written a bunch of CFML code that retrieved all the
employees for a certain market (and other restrictions), and then I proceeded
to build an array of structures where each element of the array was an employee
and the structure members of that array element was all the vital information
about that employee. I would then loop over the structure looking for employees
who matched more closely the criteria I was looking for.

Now, I'm trying to do the same sort of thing with CFC's only slightly more
complex and a bit more granular. I created an employee class with three
methods: getEmployeeSkills, getEmployeeAddress, and getEmployeePhone. I have a
class called "nurse" since a nurse is a type of employee. I start by creating a
nurse object from my nurse class which inherits the methods from the employee
class. My nurse object returns an array each element of which contains a
structure that represents a nurse. Some of the structure members contain a
simple piece of data (like first name, last name) and others contain more
complex data. For instance, the addresses structure member is an object which
is created from the getEmployeeAddress method of the employee class, and it
returns another array each element of which is a structure containing the
different pieces of an address: address line 1, address line 2, address
type(home, billing, work, etc.), City, State, Zip.

This is all started by a simple CMFL page that contains a line to create the
nurse object and another line to dump the nurse object to screen:

<CFSet nurse = CreateObject('component', 'cfcs.nurse').init()>
<CFDump var="#nurse#">

this whole process takes just over a minute. That's just too long. So I'm
trying to find out if I'm missing something in the way that I'm approaching
this OO concept or the concept of CFCs. My hope was to be able to access these
employees in a manner such as: nurse[1].addresses[1].city

Am I going about this in even remotely the right way? Any advice would be
appreciated.

Thanks.
-Chris

[Symantec]

Have you considered using a query or query of queries to filter down the inital list of possibles. It might be faster.

[mpwoodward *TMM*]

I'll jump in with a aouple of general comments and suggestions.

g1zm0guy wrote:

> Now, I'm trying to do the same sort of thing with CFC's only slightly more
> complex and a bit more granular. I created an employee class with three
> methods: getEmployeeSkills, getEmployeeAddress, and getEmployeePhone. I have a
> class called "nurse" since a nurse is a type of employee.

Are you sure you want to have a completely separate nurse class? Maybe
you need this for some reason, but depending on what you're doing with
this you might consider that a nurse is really a "role" of an employee
rather than a truly independent class. I only mention that because if
you start doing this for every type of employee you'll likely have a lot
of unnecessary object proliferation.

> I start by creating a
> nurse object from my nurse class which inherits the methods from the employee
> class. My nurse object returns an array each element of which contains a
> structure that represents a nurse. Some of the structure members contain a
> simple piece of data (like first name, last name) and others contain more
> complex data. For instance, the addresses structure member is an object which
> is created from the getEmployeeAddress method of the employee class, and it
> returns another array each element of which is a structure containing the
> different pieces of an address: address line 1, address line 2, address
> type(home, billing, work, etc.), City, State, Zip.
>
> This is all started by a simple CMFL page that contains a line to create the
> nurse object and another line to dump the nurse object to screen:
>
> <CFSet nurse = CreateObject('component', 'cfcs.nurse').init()>
> <CFDump var="#nurse#">
>
> this whole process takes just over a minute. That's just too long. So I'm
> trying to find out if I'm missing something in the way that I'm approaching
> this OO concept or the concept of CFCs. My hope was to be able to access these
> employees in a manner such as: nurse[1].addresses[1].city

Are you saying it takes over a minute to create a *single* nurse object?
If that's the case you'd really have to elaborate on what you're doing
or post some additional code so we can better try and evaluate what's
going on here.

If I'm understanding what you're doing, it sounds like you're creating
an object to hold arrays of structures about all nurses. I guess my
question would be why? Whenever you do something like "give me all
nurses" and you create an object to hold the results you're really
reinventing the wheel--that's what the query object is for. No need to
make your own container for this type of data in most cases, and it will
definitely be a heavyweight process compared to the query object.

To use your nurse object as an example, I've seen people do a basic
search that hits the database, and then they'll take their query object,
loop over it and instantiate an object for each database record, shove
that into an array, and then use that array of objects to output basic
information about each nurse like name, etc. Don't do that! :-) It's
a very expensive process and you don't gain anything in the end over
using the query object directly.

Don't get me wrong, I do pretty much all OO these days, but it's always
good to use CF's built-in objects for their intended purpose,
particularly where the query object is concerned.

Matt

--
Matt Woodward
Team Macromedia - ColdFusion

[g1zm0guy]

Yes, I tried that, but the Query took quite a while to run. Unfortunately, I'm
in an environment where it is not possible for me to add indices to my tables.
I'm dealing with old FoxPro 2.6 tables and the indexes get rebuilt nightly by a
process that I cannot control (owned by another vendor).

I was talking to someone else about this, and I think I may just do what he
called "LazyLoading". I'm going to narrow down my list of employees as much as
I can, and then get the granular detail only when I need it. Perhaps that will
be faster. I don't know, I'm still trying to get my mind around it a bit.

Any other comments or advice are welcome. I'm trying to get over my learning
curve. :-)

Thanks.

[lad4bear]

Hi there,

CFC's are pretty slow to instantiate especially when compared to structures.
So the simple answer is don't use them. The more complex answer is don't use
them for small grained objects where you would need to instantiate a lot of
them. Instead use them for larger grained objects or when you need to
instantiate less of them (one or two)

For example

EmployeeDataGateway - Contains all data-acces code (including sql) for your
employee table. Return query or array of structs. An array of Employee CFC's
would kill performance. I generally provide select (returns details for 1
employee), insert, update, delete and find(returns details for filtered group
of employees)

EmployeeCollection - Encapsulates filtered list of employees and business
logic that applies to the collection as a whole. I generally use this when I
want to provide a list of employyes to choose from

EmployeeEntity - Encapsulate a single employee and associated business logic
that applies only to the employee. I generally use this once I've selected an
employee from a list.

There is probably a better way to do this but it seems to be working well for
me and impact on performance is negligible,

Hope this helps,

Peter (aka lad4bear)

[g1zm0guy]

Matt,

> Are you sure you want to have a completely separate nurse class?

I don't really know. I was working from an example that I found in an article
I found on Hal Helm's website. His basic example was that you have a class
called "Car" and then another one called called "Sports Car" that extended
"Car".
(see his article here:
[url]http://www.halhelms.com/index.cfm?fuseaction=newsletters.show&issue=060204 _inter[/url]
faces1)

So, I'm not sure I'm doing it right, but at least that part made a certain
amount of sense.

> If I'm understanding what you're doing, it sounds like you're creating
> an object to hold arrays of structures about all nurses. I guess my
> question would be why? Whenever you do something like "give me all
> nurses" and you create an object to hold the results you're really
> reinventing the wheel--that's what the query object is for. No need to
> make your own container for this type of data in most cases, and it will
> definitely be a heavyweight process compared to the query object.

Matt, I think that the general reason used structures in my original code and
am trying to do something similar now with objects is because, there are times
when I will have to cross data sources. An employees data (in my specific
instance) is not organized very well. Some of the data is in old FoxPro tables
and some of it is in AS400 DB2 tables. Eventually, when I'm completely done
everything will be organized nicely and on a single database (probably the DB2
stuff), but getting information from a few queries on different data sources
and then storing the information in a structure was not only an easy way for me
to understand what I had, but also an easy way to access the data later on.

Maybe there's a better way. I don't know.

> To use your nurse object as an example, I've seen people do a basic
> search that hits the database, and then they'll take their query object,
> loop over it and instantiate an object for each database record, shove
> that into an array, and then use that array of objects to output basic
> information about each nurse like name, etc. Don't do that! :-) It's
> a very expensive process and you don't gain anything in the end over
> using the query object directly.

Yeah, I definitely don't want to do anything this drastic! :-P A part of the
idea was that I wanted to be able to access an employee's information by saying
something like:

janitor[1].skills.mopping
or
assistant[1].skills.typing = 120 // set the first administrative
assistant's typing skill = 120 wpm.

That sort of thing. I was thinking about how JavaScript treats an object like
the elements array, and sort of trying to mimic that. Don't know if that's the
thing to do.

[g1zm0guy]

Peter,

> EmployeeDataGateway - Contains all data-acces code (including sql) for your
> employee table. Return query or array of structs. An array of Employee CFC's
> would kill performance. I generally provide select (returns details for 1

employee),

> insert, update, delete and find (returns details for filtered group of

employees)

By "find" here are you talking about a method that you create that your
EmployeeDataGateway class contains? (assuming, of course, that it is a class).

>
> EmployeeCollection - Encapsulates filtered list of employees and business
> logic that applies to the collection as a whole. I generally use this when

I want

> to provide a list of employees to choose from

> EmployeeEntity - Encapsulate a single employee and associated business
> logic that applies only to the employee. I generally use this once I've

selected

> an employee from a list.

I'm interested in this idea. It sounds a bit like what I'm trying to do. Could
you perhaps elaborate for me a bit?

[mpwoodward *TMM*]

g1zm0guy wrote:

> Matt,
>

> > Are you sure you want to have a completely separate nurse class?

>
> I don't really know. I was working from an example that I found in an article
> I found on Hal Helm's website. His basic example was that you have a class
> called "Car" and then another one called called "Sports Car" that extended
> "Car".
> (see his article here:
> [url]http://www.halhelms.com/index.cfm?fuseaction=newsletters.show&issue=060204 _inter[/url]
> faces1)
>
> So, I'm not sure I'm doing it right, but at least that part made a certain
> amount of sense.

Right, it may or may not make sense--so I'm really just asking the
question more than telling you that you don't need to do this. Hal's
also written articles about using roles to avoid unnecessary object
proliferation, so it just depends on the situation. If there isn't
anything particularly unique to the nurse employee as opposed to the
generic employee object (i.e. if you can represent skills in some
generic way and don't need an actual object attribute for nurse-specific
skills) you might be better off with a generic employee object and a tpe
or role attribute to cover whether it's a nurse or a programmer.

> Matt, I think that the general reason used structures in my original code and
> am trying to do something similar now with objects is because, there are times
> when I will have to cross data sources.

Sure, but you still might be better off combining the data into a single
query object. Again *might* being the operative word. I only bring
that up because using the objects that are native to CF and designed for
this specific purpose will likely perform better even if it takes a bit
of finagling to get them created in the first place.

Just some additional thoughts--in the end you have to do what makes the
most sense given your situation.

Matt
--
Matt Woodward
Team Macromedia - ColdFusion

[g1zm0guy]

Matt,

I've thought about this "role" concept, and looked at my data. I don't think
there's anything specific to a nurse that couldn't also be applied to an
accountant, or a valet parking attendant, or whatever. So, I probably will
scrapp the separate class thing. I appreciate the input you've given me. I'm
really new to object orientation (much less oo in cf), and I've enjoyed your
help. Any other tips you may have for me, feel free to pass on the knowledge!
:-)

Thanks
Chris