c++ - copy and swap technique uses copy constructor inside assignment operator function -

i reading "effective c++ scott meyers", in item 11 recommending use "copy , swap" technique inside assignment operator:

widget& widget::operator=(const widget &rhs) {     widget temp(rhs); // copy constructor     swap(temp); //swap *this     return *this; } 

but in item 12 written:

it makes no sense have copy assignment operator call copy constructor.

i think item 11 , item 12 contradictory. understanding incorrectly?

in 2 citations of "effective c++ scott meyers" mention 2 different aspects discussed.

• in code fragment in item 11 scott shows 1 of ways implement assignment operator.
• in item 12 citation mention deals avoiding code duplication between assignment operator , copy constructor. 1 paragraph above citation says:

the 2 copying functions have similar bodies, , may tempt try avoid code duplication having 1 function call other.

my understanding of part of item 12 this: if try write below (to have copy assignment operator call copy constructor) wrong:

prioritycustomer::prioritycustomer(const prioritycustomer& rhs) : customer(rhs),   // invoke base class copy ctor   priority(rhs.priority) {   logcall("prioritycustomer copy constructor"); }  prioritycustomer& prioritycustomer::operator=(const prioritycustomer& rhs) {   logcall("prioritycustomer copy assignment operator");   this->prioritycustomer(rhs); // line wrong!!!   return *this; }