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2015-12-25 19:42

Chapter 4: Writing your first Rapid-Q Application

Rapid-Q Documentation by William Yu (c)1999	Chapter 4

4. Writing your first Rapid-Q Application

Let's jump right into writing Windows applications in Rapid-Q! There will be a simple step-by-step guide, along with the complete source code listing at the end of this chapter.

4.1 Deciding on what to write

We're not going to write a simple "Hello World!" demo, nor are we going to write a web browser, we'll start with something meaningful, yet simple to write. Let's write a simple form based database type program. Some of the concepts we'll learn is form handling, event handling, and using the components, QEDIT, QBUTTON, QFORM, QLABEL, and QLISTBOX. Here's what our finished application should look like, you can modify the interface to your liking (if you're comfortable you know what you're doing).

It may look like a lot, but honestly, the source code is less than 100 lines! Most of the time spent is used designing the layout.

4.2 Designing the form

You can almost see the components that we'll need. One QFORM, 2 QBUTTONs, 4 QEDITs, 4 QLABELs, and finally 1 QLISTBOX. First of all, we need a Window (that's our QFORM). So let's type that in:

           DIM MainForm AS QFORM

           MainForm.Center
           MainForm.Caption = "My First Application"
           MainForm.Height = 340
           MainForm.Width = 350
           MainForm.ShowModal    '-- Display form

If you entered all this correctly, you should see an empty Window, with the same geometry as the above diagram. One thing to notice is that we're not using MainForm.Left or MainForm.Top because when the MainForm is centered, it is automatically calculated for us. All we really need is to supply the width and height of our Window.

All right, now that we have our Window, we'll have to add controls to it. You should place the following code BEFORE the line MainForm.ShowModal. For the sake of argument, let's begin by adding some labels to our Window.

       DIM NameLabel AS QLABEL, AddrLabel AS QLABEL
       DIM CityLabel AS QLABEL, PhLabel AS QLABEL

           NameLabel.Parent = MainForm
           NameLabel.Caption = "Name:"
           NameLabel.Top = 13
           NameLabel.Left = 25
           AddrLabel.Parent = MainForm
           AddrLabel.Caption = "Address:"
           AddrLabel.Top = 38
           AddrLabel.Left = 25
           CityLabel.Parent = MainForm
           CityLabel.Caption = "City:"
           CityLabel.Top = 63
           CityLabel.Left = 25
           PhLabel.Parent = MainForm
           PhLabel.Caption = "Phone #:"
           PhLabel.Top = 88
           PhLabel.Left = 25

We're creating 4 label components, and we're going to use MainForm as our container for these components, hence the Parent = MainForm association. If for example, we created a QPANEL on our form, it can also act as a container for any of our controls. But we won't get into that until later. For the moment, take some time to digest the above code and add it to our previous listing.

We now have our Window, our 4 labels, now let's add the 4 edit controls to our application.

       DIM NameEdit AS QEDIT, AddrEdit AS QEDIT
       DIM CityEdit AS QEDIT, PhEdit AS QEDIT

           NameEdit.Parent = MainForm
           NameEdit.Left = 70
           NameEdit.Top = 10
           NameEdit.Width = 230
           AddrEdit.Parent = MainForm
           AddrEdit.Left = NameEdit.Left
           AddrEdit.Width = NameEdit.Width
           AddrEdit.Top = 35
           CityEdit.Parent = MainForm
           CityEdit.Left = NameEdit.Left
           CityEdit.Width = NameEdit.Width
           CityEdit.Top = 60
           PhEdit.Parent = MainForm
           PhEdit.Left = NameEdit.Left
           PhEdit.Width = NameEdit.Width
           PhEdit.Top = 85

Looks familar doesn't it? It's the same idea as our QLABELs, the biggest thing is correct placement on the form. In the above example, we're aligning all the QEDIT controls just after the QLABELs. Again, take some time to digest the above code and add it to our existing code.

All that's left is to add our 2 buttons and one listbox control. Here's how we do that:

       DIM AddButton AS QBUTTON, ClearButton AS QBUTTON
       DIM ListBox AS QLISTBOX

           AddButton.Parent = MainForm
           AddButton.Left = 70
           AddButton.Top = 115
           AddButton.Width = 110
           AddButton.Caption = "&Add to Database"
           ClearButton.Parent = MainForm
           ClearButton.Left = 190
           ClearButton.Top = 115
           ClearButton.Width = 110
           ClearButton.Caption = "&Clear Database"

           ListBox.Parent = MainForm
           ListBox.Top = 150
           ListBox.Left = 70
           ListBox.Width = 230
           ListBox.Height = 150

Cut & Paste, and voila! Wow, we now have a form which looks exactly like the diagram above (section 4.1). Run it, fool around with it for a while, then return back, there's still two more things to implement.

4.3 Handling Events

As you can see, the above code just flashes us with a nice user interface, but nothing to back it up with. If you tried clicking on the buttons, they do nothing. You'll have to write your event handler to handle a button click. Here's how:

           AddButton.OnClick = AddButtonClick

That it? Well, that's part of it, the OnClick event handler will transfer execution to the subroutine we named AddButtonClick. Now we'll have to go and write our subroutine. Just make sure you include the subroutine below, before adding the above code.

           SUB AddButtonClick
               IF ListBox.ItemCount > 0 THEN
                  '-- Add a nice separator
                  ListBox.AddItems "--------------------------"
               END IF
               ListBox.AddItems NameEdit.Text, AddrEdit.Text, _
                                CityEdit.Text, PhEdit.Text
           END SUB

Well, now we're getting somewhere. Whenever the user clicks on the add button, the code above gets executed. As you can see, all it does is add the text fields to our listbox. If you didn't already know, the underscore '_' character can be used in Rapid-Q to split up long lines. We're almost done, now we'll add an event handler for the other button.

           SUB ClearButtonClick
               ListBox.Clear
           END SUB

           ClearButton.OnClick = ClearButtonClick

Whew, if you counted all the lines, it is well below 100! Our application is now complete, you can play with it, add stuff to it, and generally learn from it.

4.4 Source code listing, in its entirety

DIM MainForm AS QFORM
DIM NameEdit AS QEDIT, AddrEdit AS QEDIT, _
    CityEdit AS QEDIT, PhEdit AS QEDIT
DIM NameLabel AS QLABEL, AddrLabel AS QLABEL, _
    CityLabel AS QLABEL, PhLabel AS QLABEL
DIM ListBox AS QLISTBOX
DIM AddButton AS QBUTTON, ClearButton AS QBUTTON

SUB AddButtonClick
  IF ListBox.ItemCount > 0 THEN
    '-- Add a nice separator
    ListBox.AddItems "--------------------------------"
  END IF
  ListBox.AddItems NameEdit.Text, AddrEdit.Text, _
                   CityEdit.Text, PhEdit.Text
END SUB

SUB ClearButtonClick
  ListBox.Clear
END SUB

NameLabel.Parent = MainForm
NameLabel.Caption = "Name:"
NameLabel.Top = 13
NameLabel.Left = 25
AddrLabel.Parent = MainForm
AddrLabel.Caption = "Address:"
AddrLabel.Top = 38
AddrLabel.Left = 25
CityLabel.Parent = MainForm
CityLabel.Caption = "City:"
CityLabel.Top = 63
CityLabel.Left = 25
PhLabel.Parent = MainForm
PhLabel.Caption = "Phone #:"
PhLabel.Top = 88
PhLabel.Left = 25

NameEdit.Parent = MainForm
NameEdit.Left = 70
NameEdit.Top = 10
NameEdit.Width = 230
AddrEdit.Parent = MainForm
AddrEdit.Left = NameEdit.Left
AddrEdit.Width = NameEdit.Width
AddrEdit.Top = 35
CityEdit.Parent = MainForm
CityEdit.Left = NameEdit.Left
CityEdit.Width = NameEdit.Width
CityEdit.Top = 60
PhEdit.Parent = MainForm
PhEdit.Left = NameEdit.Left
PhEdit.Width = NameEdit.Width
PhEdit.Top = 85

AddButton.Parent = MainForm
AddButton.Left = 70
AddButton.Top = 115
AddButton.Width = 110
AddButton.Caption = "&Add to Database"
AddButton.OnClick = AddButtonClick
ClearButton.Parent = MainForm
ClearButton.Left = 190
ClearButton.Top = 115
ClearButton.Width = 110
ClearButton.Caption = "&Clear Database"
ClearButton.OnClick = ClearButtonClick

ListBox.Parent = MainForm
ListBox.Top = 150
ListBox.Left = 70
ListBox.Width = 230
ListBox.Height = 150

MainForm.Center
MainForm.Caption = "My First Application"
MainForm.Height = 340
MainForm.Width = 350
MainForm.ShowModal

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