How Can You Implement a Virtual `operator

Overcoming the Virtual Operator<< Conundrum

In an attempt to implement a virtual << operator, the following code results in a compiler error:

<code class="cpp">virtual friend ostream &amp; operator<<(ostream&amp; os,const Advertising&amp; add);</code>

The Root of the Issue

The defined operator<< is a free function, disabling its qualification as virtual due to the absence of a receiver object. To achieve the desired virtual functionality, the operator needs to be defined as a class member.

The Problem with Direct Definition

Defining operator<< as a class member poses a different issue. The operands will be reversed, causing complications when attempting to output an object:

<code class="cpp">MyClass myObject;
myObject << cout; // Legal but not our intended usage</code>

The Solution: Indirect Approach

To navigate these challenges, introduce an additional virtual function:

<code class="cpp">class MyClass {
public:
    virtual void print(ostream&amp; where) const;
};</code>

Then, redefine operator<< as a free function, leveraging the new virtual function:

<code class="cpp">ostream&amp; operator<< (ostream&amp; out, const MyClass&amp; mc) {
    mc.print(out);
    return out;
}</code>

This setup allows the operator<< free function to maintain the correct parameter order while enabling customization of the output behavior in subclasses through the print() function.

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