在 class 构造函数中使用结构变量

Question

struct Date
{
    int year;
    int month;
    int day;
};

class Person
{
private:
    string firstName;
    string lastName;
    Date dOB;
public:
    Person();
    Person(const string& f, const string& l, const Date& d);
};

Person::Person() : firstName("None"), lastName("None"), dOB(dOB.day(0),dOB.month(0), dOB.year(0)) {}

I have a Struct Date with 3 variables day, month, year. Below, in the class Person, I am using Date for the constructor. But when I set the day, month and year = 0 it shows error that I have that expression must have pointer-to function type? What is my problem here? How can I fix it?

Answer 1

The compiler thinks the syntax dOB.day(0) is a function call.

Instead of naming the members, you can write it like this:

Person::Person() : firstName("None"), lastName("None"), dOB{0,0,0} {}

where each member of dOB gets initialized to 0.

Here's a demo .

Answer 2

Add a CTOR to your Date struct:

Date(int day, int month, int year) : year(year), month(month), day(day) {}

Use it:

Person::Person() : firstName("None"), lastName("None"), dOB(0, 0, 0) {}

Or:

Person::Person(const string& f, const string& l, const Date& d) : dOB(d) { /*...*/ };

Answer 3

Your Date struct is Aggregate type - read for Aggregate

you can use either direct initialization or list initialization

Person::Person() : firstName("None"), lastName("None"), dOB(0, 0, 0) {} // direct initialization


Person::Person() : firstName("None"), lastName("None"), dOB{0, 0, 0} {} // list initialization

Answer 4

Aboves already included two ways of intializing your dOB struct.

However if you only want a default ctor for your Person class, you don't even need to init dOB yourself, as int would be auto init to 0 , and dOb would be auto initialized to {0, 0, 0}