BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Define a property to pass an array          BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.misc View previous topic :: View next topic   Author Message Frank Guest Posted: Wed Dec 24, 2003 2:12 pm    Post subject: Define a property to pass an array I need to pass a value from one Form to a second Form called by the first. I implemented a suggestion to define a property like the following: property Fullpath: string read fFullpath write fFullpath; In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? Back to top J French Guest Posted: Wed Dec 24, 2003 3:47 pm    Post subject: Re: Define a property to pass an array On Wed, 24 Dec 2003 14:12:06 GMT, "Frank" <iuesei (AT) virgilio (DOT) it> wrote: Quote: I need to pass a value from one Form to a second Form called by the first. I implemented a suggestion to define a property like the following: property Fullpath: string read fFullpath write fFullpath; In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? In my version of Delphi (D4 Pro) - this is something that is sadly lacking The simple hack is to create your own Type - TDynStrArray It would be nice if it were standardized (You can pass Arrays that are Dynamic or not, but SetLength() is no use within the Procedure/Function) Back to top Rick Carter Guest Posted: Wed Dec 24, 2003 11:51 pm    Post subject: Re: Define a property to pass an array "Frank" <iuesei (AT) virgilio (DOT) it> wrote Quote: This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? See online help for Variant Arrays. If you're using Delphi 6, download and apply the patches first before doing any serious work with variants. Rick Carter Chair, Paradox/Delphi SIG, Cincinnati PC Users Group Back to top VBDis Guest Posted: Sat Dec 27, 2003 10:15 pm    Post subject: Re: Define a property to pass an array Im Artikel <W8hGb.4423$_P.141622 (AT) news4 (DOT) tin.it>, "Frank" <iuesei (AT) virgilio (DOT) it> schreibt: Quote: In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? A TStringList (or TList) type might be the simplest solution. DoDi Back to top Frank Guest Posted: Sun Dec 28, 2003 10:27 am    Post subject: Re: Define a property to pass an array This could be a good idea. But how I define the property for a TStringList if I did the following for a string? property Fullpath: string read fFullpath write fFullpath; "VBDis" <vbdis (AT) aol (DOT) com> ha scritto nel messaggio news:20031227171505.12631.00003744 (AT) mb-m28 (DOT) aol.com... Quote: Im Artikel <W8hGb.4423$_P.141622 (AT) news4 (DOT) tin.it>, "Frank" [email]iuesei (AT) virgilio (DOT) it[/email] schreibt: In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? A TStringList (or TList) type might be the simplest solution. DoDi Back to top Nicholas Sherlock Guest Posted: Sun Dec 28, 2003 11:05 pm    Post subject: Re: Define a property to pass an array var ffullpath:tstringlist; property fullpath:tstringlist read ffullpath write ffullpath; Cheers, Nicholas Sherlock Frank wrote: Quote: This could be a good idea. But how I define the property for a TStringList if I did the following for a string? property Fullpath: string read fFullpath write fFullpath; "VBDis" <vbdis (AT) aol (DOT) com> ha scritto nel messaggio news:20031227171505.12631.00003744 (AT) mb-m28 (DOT) aol.com... Im Artikel <W8hGb.4423$_P.141622 (AT) news4 (DOT) tin.it>, "Frank" [email]iuesei (AT) virgilio (DOT) it[/email]> schreibt: In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? A TStringList (or TList) type might be the simplest solution. DoDi Back to top Bruce Roberts Guest Posted: Mon Dec 29, 2003 5:51 am    Post subject: Re: Define a property to pass an array "J French" <erewhon (AT) nowhere (DOT) com> wrote Quote: On Wed, 24 Dec 2003 14:12:06 GMT, "Frank" <iuesei (AT) virgilio (DOT) it> wrote: I need to pass a value from one Form to a second Form called by the first. I implemented a suggestion to define a property like the following: property Fullpath: string read fFullpath write fFullpath; In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? In my version of Delphi (D4 Pro) - this is something that is sadly lacking The simple hack is to create your own Type - TDynStrArray Its not a hack, its simply the way Delphi works because of its strong typing. Quote: It would be nice if it were standardized I'm at a loss by what you mean by "standardized". Declaring a type is the standard way of doing things. It certainly prevents mistakes that can occur when one attempts to assign a value of a different type which just happens to have the same base type. Quote: (You can pass Arrays that are Dynamic or not, but SetLength() is no use within the Procedure/Function) This is not really correct. One can pass open array parameters. In which case one cannot alter the length of the formal parameter. One can also pass dynamic array types. In which case, presuming that the parameter is passed by reference, one can alter their length. The confusion is that the syntax for an open array parameter is the same for the declaration of a dynamic array. Type tDynStrArray = array of string; is a dynamic array. While procedure foo (x : array of string); declares x as an open array parameter. Not the same thing. But one can do procedure foo (var x : tDynStrArray); and then, in the body of foo do SetLength (x, 12); without any problem. What the compiler insists on is that the author be explicit about the types of data being referenced and passed around. For those used to less rigorous languages this may seem, at first, to be quite a burden. Work on any significant project for a while, especially one involving more than one author, to appreciate how truly beneficial this strong typing is. Back to top J French Guest Posted: Mon Dec 29, 2003 9:28 am    Post subject: Re: Define a property to pass an array On Mon, 29 Dec 2003 00:51:14 -0500, "Bruce Roberts" <ber (AT) bounceitattcanada (DOT) xnet> wrote: Quote: "J French" <erewhon (AT) nowhere (DOT) com> wrote in message news:3fe9b3d3.32160879 (AT) news (DOT) btclick.com... On Wed, 24 Dec 2003 14:12:06 GMT, "Frank" <iuesei (AT) virgilio (DOT) it> wrote: I need to pass a value from one Form to a second Form called by the first. I implemented a suggestion to define a property like the following: property Fullpath: string read fFullpath write fFullpath; In the calling Form, I initialize the Fullpath variable with the value I need, and the called Form uses it. This is ok for strings, but I need to pass a dynamic array. Can I do this and how do I define a correct property ? In my version of Delphi (D4 Pro) - this is something that is sadly lacking The simple hack is to create your own Type - TDynStrArray Its not a hack, its simply the way Delphi works because of its strong typing. It would be nice if it were standardized I'm at a loss by what you mean by "standardized". Declaring a type is the standard way of doing things. It certainly prevents mistakes that can occur when one attempts to assign a value of a different type which just happens to have the same base type. <snip> What I really mean is a type declared in the libraries - so everybody used the same 'declaration' I'm pretty keen on Strong Typing - but also nervous about things not being consistent Back to top Bruce Roberts Guest Posted: Tue Dec 30, 2003 7:16 pm    Post subject: Re: Define a property to pass an array "J French" <erewhon (AT) nowhere (DOT) com> wrote Quote: What I really mean is a type declared in the libraries - so everybody used the same 'declaration' It would be nice if the Help contained all of the visible type declarations in the VCL. I've learned to check Windows, SysUtils, and other units before defining my own generic types. The only danger, of course, is that the VCL authors are free to alter their declarations. So one must be judicious in their use of VCL type declarations. Back to top J French Guest Posted: Tue Dec 30, 2003 8:28 pm    Post subject: Re: Define a property to pass an array On Tue, 30 Dec 2003 14:16:12 -0500, "Bruce Roberts" <ber (AT) bounceitattcanada (DOT) xnet> wrote: Quote: "J French" <erewhon (AT) nowhere (DOT) com> wrote in message news:3feff289.70050559 (AT) news (DOT) btclick.com... What I really mean is a type declared in the libraries - so everybody used the same 'declaration' It would be nice if the Help contained all of the visible type declarations in the VCL. I've learned to check Windows, SysUtils, and other units before defining my own generic types. The only danger, of course, is that the VCL authors are free to alter their declarations. So one must be judicious in their use of VCL type declarations. That had never occurred to me - an unpleasant thought .... would they be so irresponsible ... Back to top VBDis Guest Posted: Wed Dec 31, 2003 11:44 am    Post subject: Re: Define a property to pass an array Im Artikel <GeyHb.13466$VW.640170 (AT) news3 (DOT) tin.it>, "Frank" <iuesei (AT) virgilio (DOT) it> schreibt: Quote: This could be a good idea. But how I define the property for a TStringList if I did the following for a string? property Fullpath: string read fFullpath write fFullpath; Retype the property and fFullpath field from :string to :TStringList. You may have to change more, e.g. destroy a previously stored list. Then you'll have to change the property to: property Fullpath: TStringList read fFullpath write SetFullpath; and implement a method procedure SetFullPath(list: TStringList); like begin fFullpath.Free; fFullpath := list; end; Or you may want to manage a private string list, so that SetFullPath adds the given list to the fFullpath list. Then you'll also want a method to clear the private list. And don't forget fFullpath := TStringList.Create in the constructor and fFullpath.Free in the destructor. While (dynamic) arrays are reference counted, a TStringList object must be destroyed explicitly. Just when passing such a list to another procedure it's good style to define, who has the ownership of that object, and who consequently is responsible for destroying the object, when it's no more used. DoDi Back to top Bruce Roberts Guest Posted: Thu Jan 01, 2004 6:00 am    Post subject: Re: Define a property to pass an array "J French" <erewhon (AT) nowhere (DOT) com> wrote Quote: That had never occurred to me - an unpleasant thought ... would they be so irresponsible ... Unlikely, but it does happen. IIRC a number of base types changed to Cardinal with D5. Shouldn't have caused any problem with code using derived types, but one never knows . Back to top VBDis Guest Posted: Sat Jan 03, 2004 5:04 am    Post subject: Re: Define a property to pass an array Im Artikel <3feff289.70050559 (AT) news (DOT) btclick.com>, [email]erewhon (AT) nowhere (DOT) com[/email] (J French) schreibt: Quote: I'm pretty keen on Strong Typing - but also nervous about things not being consistent I often miss predefined integer standard types, signed and unsigned, with a specific byte count, usable when reading binary records from files, and in other places. Many people define such types, but unfortunately everybody uses a different naming convention. The current Delphi types, like SmallInt and ShortInt, are more a source of confusion than a clarification of the actual size of such types. 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