BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Vectors for components and a problem          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) View previous topic :: View next topic   Author Message Mauro Guest Posted: Sun Jan 25, 2004 11:38 am    Post subject: Vectors for components and a problem Hi all, I would like to have a vector of TLabel. it's no problem to create and manage them. But if I do it, I will have an other problem that is already solved by you, I think. My amount of labels depends on the program way that is executed. This means that I could have 20 or 50 labels. As I do for every new label a push_back(), the place in a vector for this label is always different. But in the runtime of a program I will have an acces to some of these labels, but have no possibility to access them directly via index like labels.begin() + X. What do you in such a case? Have I to fill the Tag property or is there another efficient way to do that? thanks in advance, Mauro Back to top Mauro Guest Posted: Sun Jan 25, 2004 11:45 am    Post subject: Re: Vectors for components and a problem I have something to add here, at the moment I have 100 pointers to a label: TLabel *labels[100]; With this method I create new labels always in the same array place. This works great, but I have unneccassery memory usage, because I don't need all 100 pointers in the same time. Mauro "Mauro" <mauro23 (AT) gmx (DOT) de> schrieb im Newsbeitrag news:4013aabb (AT) newsgroups (DOT) borland.com... Quote: Hi all, I would like to have a vector of TLabel. it's no problem to create and manage them. But if I do it, I will have an other problem that is already solved by you, I think. My amount of labels depends on the program way that is executed. This means that I could have 20 or 50 labels. As I do for every new label a push_back(), the place in a vector for this label is always different. But in the runtime of a program I will have an acces to some of these labels, but have no possibility to access them directly via index like labels.begin() + X. What do you in such a case? Have I to fill the Tag property or is there another efficient way to do that? thanks in advance, Mauro Back to top Hans Galema Guest Posted: Sun Jan 25, 2004 4:17 pm    Post subject: Re: Vectors for components and a problem Mauro wrote: Quote: TLabel *labels[100]; This works great, but I have unneccassery memory usage, because I don't need all 100 pointers in the same time. 400 bytes are not that much to worrt about. But to keep it clean, try: int nlabels = 25; TLabel **labels; labels = new TLabel* [nlabels]; int labelnr = - 1; while ( ++labelnr < nlabels ) labels [labelnr] = new TLabel ( this ); // use labelnr = -1; while ( ++labelnr < nlabels ) delete labels [labelnr]; delete [labels]; Hans. Back to top Hans Galema Guest Posted: Sun Jan 25, 2004 6:08 pm    Post subject: Re: Vectors for components and a problem Hans Galema wrote: Quote: delete [labels]; Oh, noo... delete [] labels; Hans. Back to top Remy Lebeau (TeamB) Guest Posted: Sun Jan 25, 2004 10:38 pm    Post subject: Re: Vectors for components and a problem "Mauro" <mauro23 (AT) gmx (DOT) de> wrote Quote: As I do for every new label a push_back(), the place in a vector for this label is always different. But in the runtime of a program I will have an acces to some of these labels, but have no possibility to access them directly via index like labels.begin() + X. It is unclear what the actual problem is exactly. Please clearify. Gambit Back to top JD Guest Posted: Mon Jan 26, 2004 5:42 am    Post subject: Re: Vectors for components and a problem "Remy Lebeau (TeamB)" <gambit47.no.spam (AT) no (DOT) spam.yahoo.com> wrote: Quote: "Mauro" <mauro23 (AT) gmx (DOT) de> wrote in message news:4013aabb (AT) newsgroups (DOT) borland.com... to access them directly via index like labels.begin() + X. It is unclear what the actual problem is exactly. Please clearify. I think he's looking for something like: labels[ x ]->Caption = "A different caption"; ~ JD Back to top JD Guest Posted: Mon Jan 26, 2004 5:43 am    Post subject: Re: Vectors for components and a problem Hans Galema <dontusethis (AT) dontusethis (DOT) nl> wrote: Quote: Hans Galema wrote: delete [labels]; Oh, noo... Had enough sleep lately? <vbg> ~ JD Back to top Remy Lebeau (TeamB) Guest Posted: Mon Jan 26, 2004 7:34 am    Post subject: Re: Vectors for components and a problem "JD" <nospam (AT) nospam (DOT) com> wrote Quote: I think he's looking for something like: labels[ x ]->Caption = "A different caption"; If that were the case, then why did he already state that using an index was not an option? Gambit Back to top JD Guest Posted: Mon Jan 26, 2004 7:44 am    Post subject: Re: Vectors for components and a problem "Remy Lebeau (TeamB)" <gambit47.no.spam (AT) no (DOT) spam.yahoo.com> wrote: Quote: "JD" <nospam (AT) nospam (DOT) com> wrote in message news:4014b6b8$1 (AT) newsgroups (DOT) borland.com... I think he's looking for something like: labels[ x ]->Caption = "A different caption"; If that were the case, then why did he already state that using an index was not an option? Oh, I see. He said: "... but have no possibility to access them directly via index like labels.begin() + X.". I read that as a syntax problem where I bet you read that as he not knowing which index value to use for which label. ~ JD Back to top Mauro Guest Posted: Mon Jan 26, 2004 10:17 am    Post subject: Re: Vectors for components and a problem It's no a technical but logical question. I had an idea yesterday nad have created a vector: vector <TLabel *> labels; Then at the begining of my program I'm reserving memory: labels.reserve(100) // Maximum 100 labels at one time Then if I have several parts of my program then I can say that if include one is executed then create 10 labels, which pointers are stored in labels(0) - labels(9), in include two I use the range 10 - 40 for 30 labels and so on... This brings me the advatage that if I have to access the labels that have been created in include one from other program part, then I know that they have the position 0 - 9 in the vector. But originally as I have posted this topic then I have thoouhgt, that i could make on every program part a push_back() to this vector. But then I would have to remove the label pointers from the vector, if they would be deleted and I would not known, at which position are my labels from program part one or program part two. So at the end, I think, that my first idea that I have described at the beginning, is ok, or not?? Regards, Marius Back to top Duane Hebert Guest Posted: Mon Jan 26, 2004 2:21 pm    Post subject: Re: Vectors for components and a problem "Mauro" <Mauro23 (AT) gmx (DOT) de> wrote Quote: It's no a technical but logical question. I had an idea yesterday nad have created a vector: vector <TLabel *> labels; Then at the begining of my program I'm reserving memory: labels.reserve(100) // Maximum 100 labels at one time In general, if you want a container that you can access by index, a vector sounds correct. If you want an index that is immutable for each entry, this sounds more like a key and a map may be better suited. Please describe what you are trying to accomplish. 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