Mach-ii for newbies - part2

Reading and manipulating data

Written by Trond Ulseth (www.waterswing.com/blog)

1. Introduction

Hello, and welcome back. This is the follow up to a part 1 (obviously), originally posted at Easycfm.com (http://tutorial345.easycfm.com/). If you did not read that one yet you probably should (or maybe not - what do I know? At any rate, I won't come after you if you don't).

A lot of things have happened since I wrote part 1. In the meantime I've been developing on my first real OO (Object Oriented) application. That application was written without using mach-ii or any other framework though.

One thing I feel I did not emphasize in part 1 (actually, looking back I see I did not mention it at all) is that the mach-ii framework is "created to help software development and maintenance using an OO style" (quote from mach-ii.info). In other words, to use and leverage the mach-ii framework you should (no - need to) understand OOP.

Remember in part 1 I suggested that even though we did not see the payoff of using mach-ii right away "we'll just have to trust that there will be some payoff for the extra work further down the road". After finishing that OO project I can definitely say that there is payback down the road. And looking at the improvements using the mach-ii framework would bring to that project had it been used, I see that the payoff would be doubled (or at least enhanced pretty much).

However - for now - OOP will not be the subject of this tutorial series. I've had a lot of positive feedback from the first part, but also some criticism. One of the critics was that I focused very much on the mach-ii.xml configuration file, while going pretty quick through the bean concept. While agreeing that understanding the bean concept is important, a bean is not a mach-ii specific subject, while the mach-ii.xml file is mach-ii specific to the highest degree. So that is the walk I'll walk and talk I'll talk for now.

Let me just quickly remind you of the disclaimer from part 1: "I am learning as I'm writing, or writing as I'm learning. I can therefore not give any guaranty that what I am doing is totally best practices, or that I have so much understanding of what I'm doing that I explain it as clear as could be possible. I'll try though to write in an easy to understand and slightly entertaining way."

Enough jabbering! Let's dive into the mach-ii waters again.

2. A short repetition

Let's just quickly go through what we learned/did in the first part.

• In the mach-ii.xml config file we define a default event.
• The default event calls a view.
• What view file to display is defined under page-views in the mach-ii.xml file
• The view file contained a form, which in turn defined a new event when submitted
• This event populated a bean cfc with the values posted from the form
• This event also notified a listener, which in turn passed the bean as an argument to a CRUD cfc.

Now do you remember the assignment I gave you at the end of part 1?

Without any further ado, here's the solution:

<event-handler event="message.create" access="public">

                        <event-bean name="message" type="MyGuestbook.model.message.message" /> 

                        <notify listener="messageListener" method="createMessage" />

                        <view-page name="mainTemplate" />

            </event-handler>

I'm pretty sure that you had that one figured out yourself.

3. Where do we go from here?

The obvious first thing to do is to get the submitted messages displayed on our page. So we need to query the database for inserted messages, and find the mach-ii way of getting the output displayed on our display page.

In the first part we used a CRUD cfc for putting a message into the database. But I also said that a CRUD should only deal with one record in the database at a time. So for queries retrieving multiple records we need to create another cfc, a so called gateway.

We write the following code, and save it as messageGateway.cfc in our model/message/ directory.

So we started out with the familiar part this time. The init method we remember from the CRUD (go back and read part 1 if you're insecure about it - I know I did).  Then the findMessage method is a good ole' SELECT * query.

Seeing that the init method here is the same as in the CRUD is a pretty good clue that the gateway also is called from a listener. So now we're going to do the same. In fact we'll do it in the same listener. So let's open up the messageListener.cfc and modify it as so: