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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-NZ link=blue vlink=purple><div class=WordSection1><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 href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a> <o:p></o:p></pre><pre>Unsubscribe: send an email to <a href="mailto:delphi-request@delphi.org.nz">delphi-request@delphi.org.nz</a> with Subject: unsubscribe <o:p></o:p></pre><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 href="mailto:delphi@delphi.org.nz">delphi@delphi.org.nz</a><o:p></o:p></pre><pre>Admin: <a href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><o:p></o:p></pre><pre>Unsubscribe: send an email to <a href="mailto:delphi-request@delphi.org.nz">delphi-request@delphi.org.nz</a> with Subject: unsubscribe<o:p></o:p></pre><p class=MsoNormal><o:p> </o:p></p></div></body></html>