overloading operator >> like std::cout

Question

I would like to create a class similar to std::cout. I know how to overload the >> and << operators, but I would like to overload the << operator so it would be input, just like in std::cout.

it should be somthing like:

class MyClass
{
   std::string mybuff;
 public:
   //friend std::???? operator<<(????????, MyClass& myclass)
   {
   }
}
.
.
.

  MyClass class;
    class << "this should be stored in my class" << "concatenated with this" << 2 << "(too)";

Thanks

Oh I just posted one: http://stackoverflow.com/questions/11515925/c-string-operator-overload/ — SwiftMango, Jul 17 '12 at 06:23

Luchian Grigore · Accepted Answer · 2012-07-17T06:25:36.400

4

class MyClass
{
    std::string mybuff;
 public:
    //replace Whatever with what you need
    MyClass& operator << (const Whatever& whatever)
    {
       //logic
       return *this;
    }

    //example:
    MyClass& operator << (const char* whatever)
    {
       //logic
       return *this;
    }
    MyClass& operator << (int whatever)
    {
       //logic
       return *this;
    }
};

edited Jul 17 '12 at 06:25

answered Jul 17 '12 at 06:13

Luchian Grigore

253,575
64
457
625

I've tried it, but I get the following error: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const char [4]' (or there is no acceptable conversion) – Mercury Jul 17 '12 at 06:19
@Mercury have you replaced `Whatever` with `const char*`? – Luchian Grigore Jul 17 '12 at 06:20
1

@Mercury also look at `std::stringstream`, it too concatenates. – Luchian Grigore Jul 17 '12 at 06:23

score 0 · Answer 2 · edited May 23 '17 at 12:04

0

I think the most general answer would be:

class MyClass
{
   std::string mybuff;
 public:
   template<class Any>
   MyClass& operator<<(const Any& s)
   {
          std::stringstream strm;
          strm << s;
          mybuff += strm.str();
   }

   MyClass& operator<<( std::ostream&(*f)(std::ostream&) )
   {
    if( f == std::endl )
    {
        mybuff +='\n';
    }
    return *this;
}
}

std::endl was pasted from Timbo's answer here

Thanks for the answers!

edited May 23 '17 at 12:04

Community

1
1

answered Jul 17 '12 at 06:40

Mercury

1,886
5
25
44

(1) If you can, make `mybuff` an `ostringstream`, that way you don't need the extra concatenation in `operator<<(Any)`. (2) Your overload for stream manipulators only handles `endl`, nothing else. This means that `std::hex` or whatever can be written to the stream, but have no effect. If `mybuff` was an `ostringstream` then you could apply the manipulator to that. Then all the usual formatting options would work and so would `endl`, no need to special-case it. – Steve Jessop Jul 17 '12 at 07:13
Can you post how the operator<< should look like? – Mercury Jul 17 '12 at 08:07

overloading operator >> like std::cout

2 Answers2