C equivalent of Java s toString

Question

I d like to control what is written to a stream  i e  cout  for an object of a custom class  Is that possible in C    In Java you could override the toString   method for similar purpose

User · Answer

As an extension to what John said  if you want to extract the string representation and store it in a std  string do this    include  lt sstream gt                Suppose a class A A a  std  stringstream sstream  sstream  lt  lt  a  std  string s   sstream str       or you could use sstream  gt  gt  s but that would skip out whitespace   std  stringstream is located in the  lt sstream gt  header

User · Answer

The question has been answered  But I wanted to add a concrete example   class Point   public        Point int theX  int theY   x theX   y theY                    Print the object       friend ostream amp  operator  lt  lt  ostream amp  outputStream  const Point amp  p   private        int x        int y      ostream amp  operator  lt  lt  ostream amp  outputStream  const Point amp  p          int posX   p x         int posY   p y          outputStream  lt  lt   x   lt  lt posX lt  lt     lt  lt  y   lt  lt posY        return outputStream      This example requires understanding operator overload

User · Answer

In C  11  to string is finally added to the standard   http   en cppreference com w cpp string basic string to string

User · Answer

In C   you can overload operator lt  lt  for ostream and your custom class   class A   public    int i      std  ostream amp  operator lt  lt  std  ostream  amp strm  const A  amp a      return strm  lt  lt   A    lt  lt  a i  lt  lt           This way you can output instances of your class on streams   A x        std  cout  lt  lt  x  lt  lt  std  endl    In case your operator lt  lt  wants to print out internals of class A and really needs access to its private and protected members you could also declare it as a friend function   class A   private    friend std  ostream amp  operator lt  lt  std  ostream amp   const A amp      int j      std  ostream amp  operator lt  lt  std  ostream  amp strm  const A  amp a      return strm  lt  lt   A    lt  lt  a j  lt  lt

User · Answer

You can also do it this way  allowing polymorphism   class Base   public     virtual std  ostream amp  dump std  ostream amp  o  const         return o  lt  lt   Base     lt  lt  b  lt  lt             private    int b      class Derived   public Base   public     virtual std  ostream amp  dump std  ostream amp  o  const         return o  lt  lt   Derived     lt  lt  d  lt  lt             private     int d     std  ostream amp  operator lt  lt  std  ostream amp  o  const Base amp  b    return b dump o

[c++] C++ equivalent of Java's toString?

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