Volume Number: 24 (2008)
Issue Number: 07
Column Tag: REALBasic
by Norman Palardy
REALbasic is a Rapid Application Develpment (RAD) tool from REALSoftware. In previous columns we've looked at it briefly and even talked with Geoff Perlmann, the CEO of REAL Software. This month we're continuing our series of articles that aim to get you started with REALbasic and show you how to be productive with it. For this series we're using the latest version of REALbasic; version 2008r1.
In this installment we're creating an application that tracks the prices of stocks. This will involve accessing the Internet to grab quotes, graphs and a database. Some of the components required are built in to REALbasic itself, and others will have to come from third parties.
In this installment we'll design the interface, the database and the windows we'll need for adding stocks to track. We'll get started writing the basics that make the whole project come together.
First, start REALbasic so you have a new project to work with.
Figure 1. REALbasic default project
As we saw last month, this default project is a fully functioning program. You could immediately run it by pressing the green Run button.
Let's consider the tasks we'll need to accomplish to make this program work the way we want.
That's a lot of things to consider so we'll tackle them one at a time. Lets start with how we show our list of stocks of interest.
In the project we created earlier, there should already be a window called Window1. Let's start by editing that window and altering its layout to turn it into one that shows our list of stocks.
Figure 2. Editing a REALbasic window
Down the left hand side is a list of the standard controls that are available in REALbasic. Note that I'm using the Professional version. The Personal version has a smaller set of controls.
In the center is the actual editor where you lay out the look of your window. On the right is the properties palette that displays the properties of the currently selected item.
First, rename this window so that at a glance, you can know which window it is. Click the window so it is selected as shown in Figure 2, and then click on the Name in the property list on the right. Name this window wStocks.
Then add a Listbox control to the window. Rename the listbox lstStocks and position and resize it so your window appears about like the one in Figure 3. Note that Figure 3 shows you the position and size of my listbox in the properties palette on the right hand side.
You'll also notice that the listbox has several lock properties set (LockLeft, LockRight, LockTop, LockBottom). These properties tell REALbasic to keep the listbox "locked" to the respective sides of the window if the window is resized.
Figure 3. Create the stock list window
If you run the project at this point you wont see much except that a window with a large white area shows up. That area is the listbox, which is empty at this point.
The question, then, is how to fill it with data and what data to fill it with.
Every control has a number of "events" that allow you provide custom code when something (an event) occurs. Different controls have different events. The list of events that exist for a control varies depending on what kind of control it is. Simple controls have few events. Timers only have one event. The listbox has a fairly long list of events. For our program let's start with just using the Open event.
This event occurs when the control is about to be shown on a window that is being opened. It occurs only once when the window is initially opened. There are other events that occur more frequently but for the start of this project we'll use this event.
One thing to be aware of is that event ordering is generally not something you want to rely on. You have no idea if the listbox Open event occurs before or after some other controls Open event. The other control may not even exist yet. So you have to be careful about how you use certain events and what you try to do in the code for that event.
If you double-click the listbox you will be shown the code editor. REALbasic also tries to be helpful and selects the most likely event you are going to want to edit. In this case that's the Change event for the list box.
Figure 4. Editing the listbox events in the stock list window
Select the Open event in the left hand pane and then add the following code :
me.ColumnCount = 3 // change the number of visible columns me.HasHeading = true // make the list box have a leading row me.Heading(0) = "Symbol" // set the heading for the first column me.Heading(1) = "Time" // set the heading for the second column me.Heading(2) = "$" // set the heading for the third column
Much of this CAN be done without writing code. If you review figure 3, you'll see that in the right hand properties pane there are settings for ColumnCount, HasHeading and InitialValue. If you set the columnCount property to 3 then the listbox will have 3 columns. If you check HasHeading then the listbox will have a heading and the setting for InitialValue will be used as the column headings. We've done these things in the Open event simply to illustrate that you can change some properties on the fly and they will take effect right away. Being able to alter the number of columns and their headings at run time will be shown in future articles.
If you run the program now, you can see that when the window opens it has 3 columns with the headings we wanted.
Now we have a way to get the display looking like what we want, so now let's see about getting some rows into it that display data.
If you look up ListBox in the built-in Language Reference, you'll see it has numerous events, properties and methods. Again, an event is some piece of code that gets run when something happen; a person selects a row, clicks a button or presses a key. Properties are the "settings" of various aspects of the control; the number of columns, which row is selected, or other display related values like the text font and size.
Methods are behaviors that the listbox will perform. These are actions like adding a row (AddRow), remove a row (RemoveRow), or ways to get data from the listbox (Cell and CellTag).
For our use AddRow is the one we need at present. At the end of the open event add the following code :
me.AddRow "AAPL" // add one symbol we're interested in watching dim newDate as new Date // create a new instance of a Date me.cell(me.LastIndex,1) = newDate.ShortDate + " " + newDate.ShortTime // add the date / time stamp me.cell(me.LastIndex,2) = format(169.73,"$,#.00") // display Apple's current value
Let's review this code closely.
me.AddRow "AAPL" // add one symbol we're interested in watching
This line adds the data for the first cell (the left most one also known as column 0) and leaves the other cells empty.
dim newDate as new Date
For the second column we want the current date and time. In order to get that information we need to create an instance of a Date object, which is conveniently initialized to the date and time from the OS when the instance was created. A Date instance is not a clock and does not automatically count forward.
me.cell(me.LastIndex,1) = newDate.ShortDate + " " + newDate.ShortTime // add the date / time stamp
Then we fill the middle cell — the one we want to contain the date and time — by using the CELL method to refer to a specific cell. Note that in order to make sure we set the correct cell in the correct row there is a convenient property called "lastIndex" that is the row number that was last added. The code says "set the last rows cell 1 to the short date and short time" which is exactly what we want.
me.cell(me.LastIndex,2) = format(169.73,"$,#.00")
For the last column, column 2, we want a value. But the listbox only knows how to display strings. So we have to take the current value of Apple's stock, 169.73, which is a number and convert it into a string that the listbox can display. Also, we want to make sure the string that the listbox displays is formatted so it looks just the way we want. To do that we use the FORMAT method which gives us control over how numbers look when they are converted to strings.
Run this now and you'll see we're making headway. We can make the listbox display data, and we can add data to it.
Next time we'll look at how to make the data that we display more dynamic and actually get it from a web based quote service like Yahoo finance.
Norman Palardy has worked with SQL databases since 1992, and has programmed in C, C++, Java, REALbasic and other languages on a wide variety of platforms. In his 15+ years of IT experience, Norman has developed innovative and award-winning applications for TransCanada Pipelines, Minerva Technologies (now XWave), Zymeta Corporation, and the dining and entertainment industry. He holds a BSc from the University of Calgary in Alberta. He's also the Vice President of the Association of REALbasic Professionals (http://www.arbp.org)
