Using it (2)
Below is the code for the cText2HTML class...
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Code (cText2HTML.cls)
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Option Explicit
Implements IConvert
Private m_sOutput As String
Private m_sSource As String
'sets the source text...
Private Property Let IConvert_SourceText(RHS As String)
'set a new value
m_sSource = RHS
End Property
Private Property Get IConvert_SourceText() As String
'get the current value
IConvert_SourceText = m_sSource
End Property
'returns the outputted text...
Private Property Get IConvert_OutputText() As String
IConvert_OutputText = m_sOutput
End Property
'the conversion procedure
Private Function IConvert_Convert() As Boolean
'pretend to convert text to HTML...
'just add a HTML header and footer + pre tags
Dim lEndPos As Long
Dim sTitle As String
m_sOutput = ""
'get the title text from the first line
'get the end of the line
lEndPos = InStr(1, m_sSource, vbCrLf)
If lEndPos <> 0 Then
'return the text in between
the title tag
sTitle = Left$(m_sSource, lEndPos
- 1)
End If
'add the HTML header
m_sOutput = "<html><head><title>"
& sTitle & "</title></head>" & vbCrLf
& "<body>"
'add the rest of the text
m_sOutput = m_sOutput & Mid$(m_sSource, lEndPos
+ 2, Len(m_sSource) - (lEndPos + 1))
m_sOutput = m_sOutput & "</body></html>"
IConvert_Convert = True
End Function
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Now that we have created the two conversion classes, we need to write some
code that uses them. First, add the following controls to a form...
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Controls (frmExample.frm)
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Type
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Name
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Properties
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| ComboBox |
cboConvert |
Style=3,List='HTML to Text'+'Text to HTML' |
| CommandButton |
cmdConvert |
Caption=Convert |
| TextBox |
txtSource |
Multiline=True |
| TextBox |
txtResult |
Multiline=True |
and then add the code below.
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Code (cText2HTML.cls)
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Option Explicit
Private Sub cmdConvert_Click()
Dim cConvert As IConvert
Select Case cboConvert.ListIndex
Case 0 'html2text
Set cConvert = New cHTML2Text
Case 1 'text2html
Set cConvert = New cText2HTML
End Select
cConvert.SourceText = txtSource.Text
'convert
If cConvert.Convert = False Then
MsgBox "Conversion failed!",
vbCritical
Else
txtResult.Text = cConvert.OutputText
End If
End Sub
Private Sub Form_Load()
cboConvert.ListIndex = 1
End Sub
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Notice that in the Select...Case statement, even though cConvert is set to
two different types of class (cHTML2Text or cText2HTML), cConvert does not have
to be declared as an Object. Instead, it is declared as IConvert, because both
the classes use that Interface. This is one of the major benefits of using polymorphism.
However, after doing all this, and running your project, you might still say,
“so what” so, in the next section, I
will try to convince you of its other benefits!
** You can download all the source code used and the example project by clicking
here **