dev-cpp-users

[Dev-C++] Copy constructor or assignment operator

[Maya <Esc...@ne...>]

Hey folks!
I am having problems grasping the meaning of 'operator=' and copy 
constructor.
In the following example
namespcace jme{
    class Name{
          std::string str;
       public:
          Name(){}
          Name(const jme::Name& rhs){ this->str = rhs.str;}
          ~Name(){}
          jme::Name& operator=(const jme::Name& rhs) {
             if(this->str == rhs.str ) {
             return *this;
          }
          this->str = rhs.str;
          return *this;
       }
    };
    class Person{
       private:
          jme::Name* name;
          Init()throw(std::bad_alloc){
             try{name = new jme::Name;}
             catch(std::bad_alloc& x){ throw;}
          }
       public:

          Person(const jme::Name& n){
             try{ Init(); }
             catch(std::bad_alloc& x){ throw; }
             name = &n; // <<== Here is the problem
         }
    }

I get an error saying: Invalid conversion 'const jme::Name*' to 'jme::Name*'

If I change the parametized c'tor to jme::Person::Person(jme::Name& n) the
constantness disapears and the program compiles, but that is not what I 
want.
What I want if the c'tor to receive a reference to a constant jme::Name.

Can someone please, help me understand what is that I am doing wrong.
-- 

FYI
http://www.astro.umd.edu/~marshall/abbrev.html

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   power to make the innocent guilty and to make the guilty
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                                 - Malcom X
* "Innocent until proven guilty", no... not in Canada!!

Re: [Dev-C++] Copy constructor or assignment operator

[Per W. <pw...@ia...>]

Please - don't send your questions to zillions of mailing lists! Select
ONE (1) for your questions. I can't see what your question have with the
gtk+ or foxgui mailing list for example.

Anyway. When the input parameter is const, you may not change it or let a
non-const pointer or reference point to it. If the assignment was legal,
you would then be able to throw away the const, thereby allowing
assignment to the original Name object.

/Per W

On Thu, 18 Dec 2003, Maya wrote:

> Hey folks!
> I am having problems grasping the meaning of 'operator=' and copy
> constructor.
> In the following example
> namespcace jme{
>     class Name{
>           std::string str;
>        public:
>           Name(){}
>           Name(const jme::Name& rhs){ this->str = rhs.str;}
>           ~Name(){}
>           jme::Name& operator=(const jme::Name& rhs) {
>              if(this->str == rhs.str ) {
>              return *this;
>           }
>           this->str = rhs.str;
>           return *this;
>        }
>     };
>     class Person{
>        private:
>           jme::Name* name;
>           Init()throw(std::bad_alloc){
>              try{name = new jme::Name;}
>              catch(std::bad_alloc& x){ throw;}
>           }
>        public:
>
>           Person(const jme::Name& n){
>              try{ Init(); }
>              catch(std::bad_alloc& x){ throw; }
>              name = &n; // <<== Here is the problem
>          }
>     }
>
> I get an error saying: Invalid conversion 'const jme::Name*' to 'jme::Name*'
>
> If I change the parametized c'tor to jme::Person::Person(jme::Name& n) the
> constantness disapears and the program compiles, but that is not what I
> want.
> What I want if the c'tor to receive a reference to a constant jme::Name.
>
> Can someone please, help me understand what is that I am doing wrong.
> --
>
> FYI
> http://www.astro.umd.edu/~marshall/abbrev.html
>
> E-Mail Policy
> http://www.vif.com/users/escalante/Email_Policy.html
>
> * You cannot exercise your power to a point of humiliation.
>                                 - Jean Chretien
>
> * The media's the most powerful entity on earth. They have the
>    power to make the innocent guilty and to make the guilty
>    innocent, and that's power.
>                                  - Malcom X
> * "Innocent until proven guilty", no... not in Canada!!
>
>
>
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