HTA
Tutorial #10HTA
Tutorial #10So, now we've created a file, time now to read it back again. The program looks like this.
<HTML>
<BODY>
<HEAD>
<title>Save</title>
<HTA:APPLICATION>
<Script Language=VBS>
sub subLoad()
dim fs
dim a
Const ForReading = 1
Set fs = CreateObject("Scripting.FileSystemObject")
Set a = fs.OpenTextFile("hello.txt", ForReading)
msgbox(a.ReadLine)
a.Close
end sub
</SCRIPT>
</HEAD>
<body scroll="no">
<INPUT TYPE="Submit" ID="btnQuit" VALUE="Quit App" onclick=self.close()>
<INPUT TYPE="Submit" ID="Read" VALUE="Read" onclick=subLoad()>
</BODY>
</HTML>
This is very similar to the previous tutorial and differs only in subroutine and it's name. The code breaks down as follows:
<HTML>
<BODY>
<HEAD>
<title>Save</title>
<HTA:APPLICATION>
<Script Language=VBS>
This is all the same as before.
sub subLoad()
A new name for a new routine
that could be integrated into a much larger program that could
include the routine in the previous tutorial.
dim fs
dim a
Some variables are created to hold all the object
references. These are local to this subroutine and cannot be
accessed by other subroutines or th main program.
Const ForReading = 1
This differs slightly from the previous one and it means
that instead of using a number, a more meaningful variable name
can be used.
Set fs = CreateObject("Scripting.FileSystemObject")
Set a = fs.OpenTextFile("hello.txt", ForReading)
Same as before except that we
are reading from the file.
msgbox(a.ReadLine)
For the sake of simplicity, I am
merely displaying the contents of the file using a msgbox which
will only read the first line of the file irrespective of how
many lines there are in the file.
a.Close
end sub
</SCRIPT>
</HEAD>
<body scroll="no">
<INPUT TYPE="Submit" ID="btnQuit" VALUE="Quit
App" onclick=self.close()>
<INPUT TYPE="Submit" ID="Read" VALUE="Read"
onclick=subLoad()>
Everything is the same as before except that the button
is called Read and the routine being called is subLoad.
The quit button still works as before.
</BODY>
</HTML>
Now it might be useful to be able to test whether a file exists or not. Here is the code.
<HTML>
<BODY>
<HEAD>
<title>Exist</title>
<HTA:APPLICATION>
<Script Language=VBS>
sub subReportFileStatus()
Dim fs, msg
Set fs = CreateObject("Scripting.FileSystemObject")
If (fs.FileExists("hello.txt")) Then
msg = "file" & " exists."
Else
msg = "file" & " doesn't exist."
End If
msgbox(msg)
End sub
</SCRIPT>
</HEAD>
<body scroll="no">
<INPUT TYPE="Submit" ID="btnQuit" VALUE="Quit App" onclick=self.close()>
<INPUT TYPE="Submit" ID="btnExist" VALUE="Exist?" onclick=subReportFileStatus()>
</BODY>
</HTML>
Now hopefully, if you've been following the whole tutorial, you'll have a good idea of what is going on here. The file object has another routine we can call that will test whether a file exists or not (see how useful objects can be) and it is simply a matter of deciding which message to display depending on the results of the IF statement.
I'll leave you with a little project to try. Could you combine the files from this tutorial with the previous one to create a program that will only create a file if it doesn't exist and only read from it if it exists. You'll have three buttons : Quit, Read and Create with the relevent routines in the code. Next time, I'll show you what it should look like and we'll try to append to a file instead of overwriting it. Have fun. Remember, send me an email if you get stuck.