BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  TList and TDateTime* Goto page 1, 2, 3  Next          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message Gallo_Teo Guest Posted: Sat Feb 11, 2006 9:03 am    Post subject: TList and TDateTime* Hi to all, i need to store some TDateTime in a list. I've done it in this way: TDateTime *t = new TDateTime(0,0,10,0); List->Add(t); As i read in some post of Gambit, it is not suggested to use it with the operator NEW. infact i have a lot of probelm with the operator like this example TDateTime *t1 = (TDateTime*)List->Items[0]; TDateTime *t2 = (TDateTime*)List->Items[1]; if i want to find the smallest i have to do if( *t1 < *t2) {....} otherwise the compiler check the pointer i think... but the real problem is with the operation because if i want to add a second to t1 i have to do TDateTime *myNewTime = new TDateTime(*t1 + TDateTime(0,0,1,0)) the compiler doesn't give any error but the sum it's not ever correct and some time t1 change but i can't understand why. so, how can i store TDateTime Objects in a TList and do perations with them? Teo Back to top JD Guest Posted: Sat Feb 11, 2006 4:03 pm    Post subject: Re: TList and TDateTime* "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote: Quote: i need to store some TDateTime in a list. I suspect that you'll get several responses because to a point, it's a matter of choice. Just off of the top of my head, I think that a TStringList might be a better choice. For example: TStringList *pList = NULL; //------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { pList = new TStringList; } //------------------------------------------------------------- __fastcall TForm1::~TForm1() { delete pList; } //------------------------------------------------------------- void __fastcall TForm1::Button1Click(TObject *Sender) { for( int x = 0; x < 10; ++x ) { pList->Add( DateTimeToStr(Now() + x) ); } for( int x = 0; x < pList->Count; ++x ) { TDateTime dt = StrToDateTime( pList->Strings[x] ); ShowMessage( DateTimeToStr(dt) ); } } //------------------------------------------------------------- Not only do you not have to worry about memory leaks when using a TList, TStringList also has an Objects property that you can use to associate a particular date with a particular object. ~ JD Back to top Liz Albin Guest Posted: Sat Feb 11, 2006 4:03 pm    Post subject: Re: TList and TDateTime* On 11 Feb 2006 07:16:32 -0700, JD wrote: Quote: Not only do you not have to worry about memory leaks when using a TList, TStringList also has an Objects property that you can use to associate a particular date with a particular object. Let me just add that if you want you can use an auto_ptr for the TStringList, and then not worry about allocation and deletion -- liz Back to top Duane Hebert Guest Posted: Sat Feb 11, 2006 5:03 pm    Post subject: Re: TList and TDateTime* "JD" <nospam (AT) nospam (DOT) com> wrote in message news:43edffd0$1 (AT) newsgroups (DOT) borland.com... Quote: "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote: i need to store some TDateTime in a list. I suspect that you'll get several responses because to a point, it's a matter of choice. My choice would be: std::list<TDateTime> DateTimeList; DateTimeList.insert(...); No casting required to access anything. No pointers to worry about cleaning up. Back to top Dennis Jones Guest Posted: Sat Feb 11, 2006 5:03 pm    Post subject: Re: TList and TDateTime* ----- Original Message ----- From: "Dennis Jones" <nospam (AT) nospam (DOT) com> Newsgroups: borland.public.cppbuilder.language.cpp Sent: Saturday, February 11, 2006 8:22 AM Subject: Re: TList and TDateTime* Quote: If you just want to change the value of one element in the list, you don't have to create a new pointer to do that. Just dereference the pointer and change the value it points to: *List->Items[0] += TDateTime(0,0,1,0); Oops, I forgot the cast: *(TDateTime *)List->Items[0] += TDateTime(0,0,1,0); That's another good reason not to use TList -- you have to remember to cast everything. With an STL container you don't have to remember/worry about casting. - Dennis Back to top Dennis Jones Guest Posted: Sat Feb 11, 2006 5:03 pm    Post subject: Re: TList and TDateTime* "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote in message news:43ed9cdb$1 (AT) newsgroups (DOT) borland.com... Quote: Hi to all, i need to store some TDateTime in a list. I've done it in this way: TDateTime *t = new TDateTime(0,0,10,0); List->Add(t); As i read in some post of Gambit, it is not suggested to use it with the operator NEW. infact i have a lot of probelm with the operator like this example TDateTime *t1 = (TDateTime*)List->Items[0]; TDateTime *t2 = (TDateTime*)List->Items[1]; Gambit's right. You should avoid storing pointers that you allocate in a TList. Not that you can't do it, but it is very difficult to manage all the pointers and make sure they all get deleted at the proper time. Quote: if i want to find the smallest i have to do if( *t1 < *t2) {....} otherwise the compiler check the pointer i think... There is nothing wrong with that, but you could also do this: TDateTime t1 = *(TDateTime*)List->Items[0]; TDateTime t2 = *(TDateTime*)List->Items[1]; if ( t1 < t2 ) {...} Quote: but the real problem is with the operation because if i want to add a second to t1 i have to do TDateTime *myNewTime = new TDateTime(*t1 + TDateTime(0,0,1,0)) the compiler doesn't give any error but the sum it's not ever correct and some time t1 change but i can't understand why. If you just want to change the value of one element in the list, you don't have to create a new pointer to do that. Just dereference the pointer and change the value it points to: *List->Items[0] += TDateTime(0,0,1,0); Quote: so, how can i store TDateTime Objects in a TList and do perations with them? Well, as others will probably suggest, don't use TList. If there is no specific reason to use TList, I'd suggest using an STL container, such as std::vector, instead. Then you won't have to allocate any memory at all: std::vector<TDateTime> List; List.push_back( TDateTime(0,0,10,0) ); List.push_back( TDateTime(0,0,11,0) ); To find the smaller of two times: if ( List[0] < List[1] ) {...} To change an existing time from the list: List[0] += TDateTime(0,0,1,0); - Dennis Back to top JD Guest Posted: Sun Feb 12, 2006 5:09 am    Post subject: Re: TList and TDateTime* Liz Albin <lizalbinNotThis (AT) yahoo (DOT) com> wrote: Quote: On 11 Feb 2006 07:16:32 -0700, JD wrote: Let me just add that if you want you can use an auto_ptr for the TStringList, and then not worry about allocation and deletion Can auto_ptr be used for something other than a local variable? ~ JD Back to top JD Guest Posted: Sun Feb 12, 2006 5:09 am    Post subject: Re: TList and TDateTime* "Duane Hebert" <spoo (AT) flarn2 (DOT) com> wrote: Quote: My choice would be: std::list<TDateTime> DateTimeList; DateTimeList.insert(...); No casting required to access anything. No pointers to worry about cleaning up. I confess to being relatively ignorant of anything std except vectors and bits but it sure does look like a better choice (presuming that one can maintain order like with an Add method). ~ JD Back to top Duane Hebert Guest Posted: Sun Feb 12, 2006 2:03 pm    Post subject: Re: TList and TDateTime* "JD" <nospam (AT) nospam (DOT) com> wrote in message news:43eeba2e$1 (AT) newsgroups (DOT) borland.com... Quote: "Duane Hebert" <spoo (AT) flarn2 (DOT) com> wrote: I confess to being relatively ignorant of anything std except vectors and bits but it sure does look like a better choice (presuming that one can maintain order like with an Add method). std::list has push_back() and push_front(). It also has a sort(). Back to top AlisdairM Guest Posted: Sun Feb 12, 2006 3:03 pm    Post subject: Re: TList and TDateTime* JD wrote: Quote: Can auto_ptr be used for something other than a local variable? Yes, but its copy semantics do make it rather awkward and unusual. For instance, I often liked to use std::auto_ptr as the return type of a factory function. Generally, you will want to use a different kind of smart pointer for storing in containers. Simplest recommendation is boost::shared_ptr, or std::tr1::shared_ptr as TR1 implementations become available. If you want to get fancy, you can go looking for other more specialized pointer libraries (I still like boost::scoped_ptr) but for general purpose daily use - shared_ptr is an incredible balancing act of efficiency vs. utility. [It works with containers, it stores 'incomplete types', it supports customer deleters to handle arrays/COM/...] -- AlisdairM(TeamB) Back to top AlisdairM Guest Posted: Sun Feb 12, 2006 3:03 pm    Post subject: Re: TList and TDateTime* Duane Hebert wrote: Quote: std::list has push_back() and push_front(). It also has a sort(). Note that sort is also a standard algorithm, for any range taking random-access iterators. The reason list has a sort function is that there are some reasonably efficient sort algorithms that can work on that data structure too, and work a whole lot better than bubble-sorting with mere bi-directional iterators! 'Normally' though, you would choose a container offering random access and the standard sort algorithm. [Just in case someone is wondering why std::list has a sort function, but not std::vector, std::deque, std::basic_string, std::tr1::array, ....] -- AlisdairM(TeamB) Back to top Gallo_Teo Guest Posted: Mon Feb 13, 2006 1:03 am    Post subject: Re: TList and TDateTime* Thanks but a have to works also with ms and use code and decode time in a string in my format. but that's not a problem thanks good idea "JD" <nospam (AT) nospam (DOT) com> ha scritto nel messaggio news:43edffd0$1 (AT) newsgroups (DOT) borland.com... Quote: "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote: i need to store some TDateTime in a list. I suspect that you'll get several responses because to a point, it's a matter of choice. Just off of the top of my head, I think that a TStringList might be a better choice. For example: TStringList *pList = NULL; //------------------------------------------------------------- __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { pList = new TStringList; } //------------------------------------------------------------- __fastcall TForm1::~TForm1() { delete pList; } //------------------------------------------------------------- void __fastcall TForm1::Button1Click(TObject *Sender) { for( int x = 0; x < 10; ++x ) { pList->Add( DateTimeToStr(Now() + x) ); } for( int x = 0; x < pList->Count; ++x ) { TDateTime dt = StrToDateTime( pList->Strings[x] ); ShowMessage( DateTimeToStr(dt) ); } } //------------------------------------------------------------- Not only do you not have to worry about memory leaks when using a TList, TStringList also has an Objects property that you can use to associate a particular date with a particular object. ~ JD Back to top Gallo_Teo Guest Posted: Mon Feb 13, 2006 3:03 am    Post subject: Re: TList and TDateTime* Hi, first to all i would like to thanks everybody. I tried to use std::list but in the help i find only few things. i understood how to create it but not how to use. it is not a class with method and property? i wrote std::list<TDateTime> DateTimeList ; TDateTime Pippo = TDateTime(0,15,0,50) ; DateTimeList.insert(Pippo); but it doesn't works. how have i to use list? thanks "Duane Hebert" <spoo (AT) flarn2 (DOT) com> ha scritto nel messaggio news:43ee1217$1 (AT) newsgroups (DOT) borland.com... Quote: "JD" <nospam (AT) nospam (DOT) com> wrote in message news:43edffd0$1 (AT) newsgroups (DOT) borland.com... "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote: i need to store some TDateTime in a list. I suspect that you'll get several responses because to a point, it's a matter of choice. My choice would be: std::list<TDateTime> DateTimeList; DateTimeList.insert(...); No casting required to access anything. No pointers to worry about cleaning up. Back to top Gallo_Teo Guest Posted: Mon Feb 13, 2006 3:03 am    Post subject: Re: TList and TDateTime* Hi Dennis, i'll try now. Thanks "Dennis Jones" <nospam (AT) nospam (DOT) com> ha scritto nel messaggio news:43ee103b$1 (AT) newsgroups (DOT) borland.com... Quote: ----- Original Message ----- From: "Dennis Jones" <nospam (AT) nospam (DOT) com Newsgroups: borland.public.cppbuilder.language.cpp Sent: Saturday, February 11, 2006 8:22 AM Subject: Re: TList and TDateTime* If you just want to change the value of one element in the list, you don't have to create a new pointer to do that. Just dereference the pointer and change the value it points to: *List->Items[0] += TDateTime(0,0,1,0); Oops, I forgot the cast: *(TDateTime *)List->Items[0] += TDateTime(0,0,1,0); That's another good reason not to use TList -- you have to remember to cast everything. With an STL container you don't have to remember/worry about casting. - Dennis Back to top Dennis Jones Guest Posted: Mon Feb 13, 2006 4:03 am    Post subject: Re: TList and TDateTime* "Gallo_Teo" <galloteo (AT) infinito (DOT) it> wrote in message news:43efe6a9$1 (AT) newsgroups (DOT) borland.com... Quote: Hi, first to all i would like to thanks everybody. I tried to use std::list but in the help i find only few things. i understood how to create it but not how to use. it is not a class with method and property? i wrote std::list<TDateTime> DateTimeList ; TDateTime Pippo = TDateTime(0,15,0,50) ; DateTimeList.insert(Pippo); but it doesn't works. how have i to use list? thanks Since you don't say what doesn't work, I can only guess that the problem is that you have not included the necessary header file: #include <list> // make sure you include this! std::list<TDateTime> DateTimeList ; TDateTime Pippo = TDateTime(0,15,0,50) ; DateTimeList.insert(Pippo); - Dennis Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Language C++) All times are GMT Goto page 1, 2, 3  Next Page 1 of 3   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.