c++ - initialize multiple variables with constructor overloading -

c++ - initialize multiple variables with constructor overloading -

let's in class constructor overloaded. can multiple info members initialized single object using different constructors of same class?

eg :

class demo{ int size; double k; public: demo(int s){ size=s; } demo(double p){ k = size+p; } void show(){ cout<<size<<" "<<k<<"\n"; } }; int main(){ demo = demo(0); = 4.7; a.show(); homecoming 0; }

is possible?

no, 1 time object constructed, it's constructed.

let's go through code , see (assuming no optimizations, please note many modern compilers copy-elision in debug or -o0 modes):

demo(0);

the code demo(0) calls demo(int s) constructor. temporary rvalue created. have temporary object values:

size = 0 k = uninitialized

demo = demo(0);

demo a created using implicit copy constructor.

we have demo object named a next values:

size = 0 k = uninitialized

a = 4.7;

because a constructed, phone call implicit assignment-operator. default assignment-operator re-create values 1 object other object. means 4.7 needs converted demo object first. possible because of demo(double p) constructor.

so temporary demo object created values:

size = uninitialized k = uninitialized + 4.7 = undefined

these values copied a , both of a's info members undefined.

possible solutions

songyuanyao's solution of using constructor multiple parameters 1 way of doing it.

using setters way.

either way, recommend having constructors provide default values data-members.

demo(int s) { size = s; k = 0.0; // or other suitable value }

here's how create setter.

void setk (double p) { k = size + p; }

you this:

int main () { demo (0) ; a.setk (4.7) ; a.show () ; homecoming 0 ; }

c++ constructor