C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  enforcing the constructor interface?          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Guest Posted: Fri Jun 02, 2006 1:50 am    Post subject: enforcing the constructor interface? Maybe I'm missing the point, please tell me; Wouldn't it be nice if constructor parameters (the interface) could be specified in abstract base classes just like with other functions? I find this a bit annoying, when making "pluginable object" interfaces. There is no way I can make sure that all pluginable objects constructors take the same parameters. 1. I could make the assumption that all constructors take no parameters, and then have a regular "init" function that does the initialization job the constructor should have done. Clients would have to remember to always call init right after construction. This is not so good, because that would mean objects could be constructed and used without being initialized / in valid state. 2. I could make the constructor private and have a regular function called something like newInstance do the actual construction work. This is a bit bad because clients would have to create objects in this non-standard way. Maybe there is a generic programming solution to enforcing the constructor interface? Cheers /Petke [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Eugene Alterman Guest Posted: Sun Jun 04, 2006 5:34 am    Post subject: Re: enforcing the constructor interface? <patrik.kahari (AT) sofe (DOT) nu> wrote in message news:1149152948.603932.238780 (AT) c74g2000cwc (DOT) googlegroups.com... Quote: Maybe I'm missing the point, please tell me; Wouldn't it be nice if constructor parameters (the interface) could be specified in abstract base classes just like with other functions? I find this a bit annoying, when making "pluginable object" interfaces. There is no way I can make sure that all pluginable objects constructors take the same parameters. 1. I could make the assumption that all constructors take no parameters, and then have a regular "init" function that does the initialization job the constructor should have done. Clients would have to remember to always call init right after construction. This is not so good, because that would mean objects could be constructed and used without being initialized / in valid state. 2. I could make the constructor private and have a regular function called something like newInstance do the actual construction work. This is a bit bad because clients would have to create objects in this non-standard way. Maybe there is a generic programming solution to enforcing the constructor interface? Use the Abstract Factory design pattern. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top petke Guest Posted: Sat Jun 10, 2006 4:39 am    Post subject: Re: enforcing the constructor interface? Thanks for your reply, that made sense. Quote: There are no pointers to constructors in C++. I had no idea. Why is this so? cheers /Petke [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Bo Persson Guest Posted: Sun Jun 11, 2006 12:48 am    Post subject: Re: enforcing the constructor interface? "petke" <patrik.kahari (AT) sofe (DOT) nu> skrev i meddelandet news:1149860777.227079.177720 (AT) f6g2000cwb (DOT) googlegroups.com... Quote: Thanks for your reply, that made sense. There are no pointers to constructors in C++. I had no idea. Why is this so? They are not explicitly banned, it is just that there is no way of forming a pointer to a constructor. If you were to try it, you would run into things like: - what is the type of the pointer? - constructors don't have unique names, they share the class name. What do you take the address of? something* pointer_to_constructor = &what_goes_here; // ?? Bo Persson [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  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.