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Sakshi J
Sakshi J

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When to use initializer list

#codenewbie #cpp #beginners
  • Define non static constant data member 
const int x; Base(): x{0} {} //also this works Base(int y): x(y) {}
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  • If you want to initialise reference variable then you can't initialise it without initialization list. 
int& _x; base(int x) : _x{x} {} //base(int x): {_x = x};
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  • You can not initialize one class data member in another class if base class does not have default constructor 
class base{ int _x; public: base(){} base(int x): _x{x} {} }; class derive{ base b; //we are here calling default constructor of base as no //parameter passed public: derived(base x) {b = x;} //called first, copy constructor called from here };
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  • You can not initialize base class data member from child class without initializer list 
class base{ int _x; public: base(int x): _x{x} {} } class derived : public base{ int _y; public: derived(int x,int y): base{x}, _y{y} {} //base{x} calls constructor of base class /* this is not gonna work, _x is private here so you must use intializer list derived(int x, int y){ _x = x; _y = y; } */ }; int main(){ derived d(4,5); return 0; }
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  • You have temp variable same as data member
  • You can not initialize data member with same name as temporary variable without initializer list 
class base{ int _x; public: base(int _x): _x{_x} {} //base(int _x) { _x = _x; } there is errorneous };
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  • Using initializer list optimize you code a little more

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