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<div class=Section1>
<p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Another
issue is you can’t use properties as parameters in a function or procedure so
you would need to store the property in a string before calling a function.
What a hassle.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Ross.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US
style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>
delphi-bounces@delphi.org.nz [mailto:delphi-bounces@delphi.org.nz] <b>On Behalf
Of </b>Jolyon Smith<br>
<b>Sent:</b> Friday, 21 January 2011 8:40 AM<br>
<b>To:</b> delphi@moorhouse.net.nz; 'NZ Borland Developers Group - Delphi List'<br>
<b>Subject:</b> Re: [DUG] Variabels stored<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Well, to be fair the same is true even if you declare it simply
as a public member. You change that public member to a public property
with read/write accessors if you need to, without changing the code that uses
the public member.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The reason to declare a member as a property is when you
positively wish to hide the implementation, not because you may wish to in the
future.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Note also that for record types, exposure as a property makes
such members harder and unintuitive to work with:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> TShape = class<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Private<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> fRect: TRect;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> public <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> property Rect: TRect read fRect write
fRect;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> end;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> shape.Rect.Left := 100; // Error: Left-side cannot
be assigned to <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>you have to instead write:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> newRect := shape.Rect;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> newRect.Left := 100;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> shape.Rect := newRect;<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>or<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> shape.Rect := Rect(100, shape.Rect.Top, shape.Rect.Right,
shape.Rect.bottom);<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>or get real nasty and expose the property by reference:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> property Rect: PRect read get_Rect; //get_Rect
returns the PRect of @fRect<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>allowing you to write:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> shape.Rect.Left := 100; // Now this is fine <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>But notice now that we have a read/write “property” that is
declared as read-only and TShape is oblivious to any changes made to its fRect.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Or you could expose each field of the record via a separate
property (not a bad idea for a TRect, but for more complex/larger records
this could be cumbersome).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This area is a bit sticky, to say the least, and I don’t think
there’s one single “right” approach – it depends very much on the specific case
at hand.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Having said AAALLL that, I have long since got in the habit of
never exposing public member variables in a class. </span><span
style='font-size:11.0pt;font-family:Wingdings;color:#1F497D'>J</span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US
style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>
delphi-bounces@delphi.org.nz [mailto:delphi-bounces@delphi.org.nz] <b>On Behalf
Of </b>David Moorhouse (DUG)<br>
<b>Sent:</b> Friday, 21 January 2011 07:33<br>
<b>To:</b> NZ Borland Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] Variabels stored<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Because a property hides the implementation details ... you
can change to read / write methods later with no change to the code that is
using the property. A public field exposes the implementation.<br>
<br>
Cheers<br>
<br>
D<br>
<br>
<br>
On 21/01/11 00:44, Ross Levis wrote: <o:p></o:p></p>
<div>
<p>I don’t see the point in doing that, unless the read/write are functions or
procedures. Just make the string public. <o:p></o:p></p>
<p> <o:p></o:p></p>
<div>
<div>
<p><b><span lang=EN-US>From:</span></b><span lang=EN-US> <a
href="mailto:delphi-bounces@delphi.org.nz">delphi-bounces@delphi.org.nz</a> [<a
href="mailto:delphi-bounces@delphi.org.nz">mailto:delphi-bounces@delphi.org.nz</a>]
<b>On Behalf Of </b>David Moorhouse (DUG)<br>
<b>Sent:</b> Thursday, 20 January 2011 11:18 PM<br>
<b>To:</b> NZ Borland Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] Variabels stored </span><o:p></o:p></p>
</div>
</div>
<p> <o:p></o:p></p>
<p>Or as field properties if you want to access them from another form ... <o:p></o:p></p>
<div>
<p>type <o:p></o:p></p>
</div>
<div>
<p> TWallaceForm = class(TForm) <o:p></o:p></p>
</div>
<div>
<p> btnOK: TButton; <o:p></o:p></p>
</div>
<p> private <o:p></o:p></p>
<div>
<p> FWallacesPrivateVar:
string; // private storage <o:p></o:p></p>
</div>
<p> public <o:p></o:p></p>
<div>
<div>
<p> property WallacesPrivateVar: string
read FWallacesPrivateVar write FWallacesPrivateVar; <o:p></o:p></p>
</div>
<div>
<div>
<div>
<p> ... <o:p></o:p></p>
</div>
</div>
</div>
<p> end; <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<p>Cheers<br>
<br>
D<br>
<br>
On 20/01/11 16:09, Conor Boyd wrote: <o:p></o:p></p>
<div>
<p>Probably as a field on the form class that you're dealing with. <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>e.g. <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>type <o:p></o:p></p>
</div>
<div>
<p> TWallaceForm = class(TForm) <o:p></o:p></p>
</div>
<div>
<p> btnOK: TButton; <o:p></o:p></p>
</div>
<div>
<p> ... <o:p></o:p></p>
</div>
<div>
<p> txtWallacesHiddenTextBox: TEdit; <o:p></o:p></p>
</div>
<div>
<p> ... <o:p></o:p></p>
</div>
<div>
<p> private <o:p></o:p></p>
</div>
<div>
<p> FWallacesPrivateVar:
string; // use this instead of your hidden text box. <o:p></o:p></p>
</div>
<div>
<p>
// Can create as many "variables" (or fields as they're known in
Delphi parlance, hence the F prefix) <o:p></o:p></p>
</div>
<div>
<p>
// of as many different types as you like. <o:p></o:p></p>
</div>
<div>
<p> ... <o:p></o:p></p>
</div>
<div>
<p> end; <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>Hope I've understood what you're asking for correctly. <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>HTH, <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>Conor <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p><b><span lang=EN-US>From:</span></b><span lang=EN-US> <a
href="mailto:delphi-bounces@delphi.org.nz">delphi-bounces@delphi.org.nz</a> [<a
href="mailto:delphi-bounces@delphi.org.nz">mailto:delphi-bounces@delphi.org.nz</a>]
<b>On Behalf Of </b>Marshland Engineering<br>
<b>Sent:</b> Thursday, 20 January 2011 3:45 p.m.<br>
<b>To:</b> <a href="mailto:delphi@delphi.org.nz">delphi@delphi.org.nz</a><br>
<b>Subject:</b> [DUG] Variabels stored </span><o:p></o:p></p>
</div>
<div>
<p>Is there a way to store variables so I can use them from one procedure
to another? <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>I have been currently storing them in hidden edit.text boxes on the
form but there must be a better way. <o:p></o:p></p>
</div>
<div>
<p> <o:p></o:p></p>
</div>
<div>
<p>Cheers Wallace <o:p></o:p></p>
</div>
<pre> <o:p></o:p></pre><pre> <o:p></o:p></pre><pre>_______________________________________________ <o:p></o:p></pre><pre>NZ Borland Developers Group - Delphi mailing list <o:p></o:p></pre><pre>Post: <a
href="mailto:delphi@delphi.org.nz">delphi@delphi.org.nz</a> <o:p></o:p></pre><pre>Admin: <a
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<p> <o:p></o:p></p>
</div>
<pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>_______________________________________________<o:p></o:p></pre><pre>NZ Borland Developers Group - Delphi mailing list<o:p></o:p></pre><pre>Post: <a
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<p class=MsoNormal><o:p> </o:p></p>
</div>
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