Notes for collection Initialization

A set is the aggregate of multiple things, including arrays, struct, and classes.

For the internal type array, we can define it like this

 

Int a [5] = {1, 2, 3, 4, 5 };

Int B [5] = {0 };

Int c [] = {1, 2, 3, 4, 5 };

 

For a struct, we can also use the {} initial method as follows:

 

Struct X

{

Int I;

Float f;

};

X x1 = {1, 1.1 };

X x2 [3] = {1, 1.1}, {2, 2.2} // The third object is initialized to 0.

 

However, if our class has private members, or all the member variables are public members but there are constructors, we cannot simply use the {} initialization method, all initialization work must be completed by the constructor.

 

# Include <iostream>

Using namespace std;

Class X

{

Public:

Int I;

Float f;

X () {cout <"default constructor" <endl ;}

X (int e, float q): I (e), f (q) {cout <"constructor" <endl ;}

 

};

Int main ()

{

// X a = {0, 0}; // compilation error, because the constructor must be called before Initialization

X B [2]; // use the default constructor for initialization

X c [3] = {X (1, 1.1), X (2, 2.2)}; // use a General constructor for initialization

Return 1;

}

Running result:

Default constructor

Default constructor

Constructor

Constructor

Default constructor

 

By identifying the differences between classes and struct initialization methods, we can think that classes are not a set in a strict sense.

 

Author: yucan1001