C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  reusing an object          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Gil Guest Posted: Thu Mar 04, 2004 11:41 am    Post subject: reusing an object Hi, I created an object set private variables in the object. I want to reuse the object but with default values. How can I do this? SomeObject so1; so1.setValue1(1); so1.setValue2(1); // I would now like a clean so1 // can I do this? so1 = new SomeObject(); Back to top Jacob Jensen Guest Posted: Thu Mar 04, 2004 12:05 pm    Post subject: Re: reusing an object I would create a function SetDefault() in SomeObject that sets all the values to their defaults. You cannot do Quote: // I would now like a clean so1 // can I do this? so1 = new SomeObject(); o you cannot do this, since new SomeObject() creates a new object in memory and returns a pointer to it, and so1 is not a pointer to a SomeObject. You could do what you want to do by declaring pointers to SomObject as such SomeObject* pso1; pso1 = new SomeObject(); // memory is allocated dynamically and is pointed at by pso1 pso1->setvalue1(1); pso1->setvalue2(1); // If you want a new "clean" object, simply delete the one created, and create a new one delete pso1; // If this is omitted, you would have garbage = memory not pointed to by anyone pso1 = new SomeObject(); // a new object is created in memory and is pointed at by pso1 Back to top Rolf Magnus Guest Posted: Thu Mar 04, 2004 12:11 pm    Post subject: Re: reusing an object Gil wrote: Quote: Hi, I created an object set private variables in the object. I want to reuse the object but with default values. How can I do this? SomeObject so1; so1.setValue1(1); so1.setValue2(1); // I would now like a clean so1 // can I do this? so1 = new SomeObject(); Try: so1 = SomeObject(); Back to top Jacob Jensen Guest Posted: Thu Mar 04, 2004 12:46 pm    Post subject: Re: reusing an object Quote: Try: so1 = SomeObject(); Does this not require implementing a copy constructor, because if the default is not good enough, you might not get all the data reinitialized. Or have got something wrong here? Jacob Back to top Buster Guest Posted: Thu Mar 04, 2004 1:11 pm    Post subject: Re: reusing an object Jacob Jensen wrote: Quote: Try: so1 = SomeObject(); Does this not require implementing a copy constructor, because if the default is not good enough, you might not get all the data reinitialized. Or have got something wrong here? It requires an assignment operator (implicit or explicit). What the operator should do is a separate issue. You are right in saying "if the default is not good enough, you might not get all the data reinitialized". It depends on your class. Quote: Jacob Back to top Rolf Magnus Guest Posted: Thu Mar 04, 2004 1:20 pm    Post subject: Re: reusing an object Jacob Jensen wrote: Quote: Try: so1 = SomeObject(); Does this not require implementing a copy constructor, because if the default is not good enough, you might not get all the data reinitialized. Or have got something wrong here? The above doesn't use the copy constructor, but the assignment operator. Often, the default for both copy constructor and assignment operator is enough. But if it's not for your class, you should implement them anyway since a class that you are not allowed to copy even though its interface claims it be copyable is broken. Alternatively, if the class is not supposed to be copied, the copy constructor and assignment operator should be declared private and not implemented. In this case, the above solution will of course not work. Another alternative (that has its own problems though and is not really a good design, so I advice against it) is to destroy and reconstruct the object in-place by doing: so1.~SomeObject(); new (&so1) SomeObject(); // #include <new> Back to top David Harmon Guest Posted: Thu Mar 04, 2004 4:19 pm    Post subject: Re: reusing an object On 4 Mar 2004 03:41:58 -0800 in comp.lang.c++, [email]brightoceanlight (AT) hotmail (DOT) com[/email] (Gil) was alleged to have written: Quote: I created an object set private variables in the object. I want to reuse the object but with default values. How can I do this? I suspect that what you actually want is to put the declaration of the variable inside your loop, so that the object is "automatically" created freshly for each iteration. 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