c++ - Does default constructor have to be provided if there are no meaningful values? -

the default constructor used automatically whenever object default or value initialized. convenient having default constructor.

but if there no meaningful default values class,

• should class still have provide default constructor?
• is there bad influence if no default constructor provided?

for example, person should have name, empty string not meaningful name:

#include <string>  class person { public:     person() : name("") {}  // have supplied?     explicit person(const std::string &n) : name(n) {} private:     std::string name; }; 

but if there no meaningful default values class, should class still have provide default constructor?

generally-speaking, no. if objects should not initialised invalid state constructor must provide means creating valid objects, means must take arguments.

you might need provide default constructor:

• if you're using serialization/deserialization framework or other runtime service creates objects , sets fields later (e.g. orm).
• if you're using std::map value-type needs default-constructor
• if you're creating simple dto objects it's okay object exist in invalid state.

is there bad influence if no default constructor provided?

if mean "no program-defined parameterless constructor", compiler create 1 you, might undesired, must use = delete modifier ensure compiler not create default constructor.

as case when objects have no default nor parameterless constructor might find containers in stl might not work class.