C ++ overloaded constructors cannot call each other.

C ++ overloaded constructors cannot call each other.

The overloaded constructors in the java class can call each other, as shown in the following code:

 1 public class TestConstructor { 2     private int value; 3  4     public TestConstructor(int value) { 5         this.value = value; 6         System.out.println("constructor1:"+this); 7     } 8  9     public TestConstructor() {10         this(10);11         System.out.println("constructor2:"+this);12     }13 14     public static void main(String[] args) {15         TestConstructor test = new TestConstructor();16         System.out.println(test.value);17         System.out.println(test);18     }19 }

The code execution result is:

Constructor1: TestConstructor @ 74a14482
Constructor2: TestConstructor @ 74a14482
10
TestConstructor @ 74a14482

It can be seen that the result is expected. The value assignment is successful and only one object is created.

 

 

Let's take a look at the C ++ implementation (header file omitted ):

 1 #include "testconstructor.h" 2 #include <QDebug> 3  4 TestConstructor::TestConstructor() 5 { 6 //    this(10); 7     TestConstructor(10); 8     qDebug()<<"constructor1:"<<this; 9 }10 11 TestConstructor::TestConstructor(int value)12 {13     this->value = value;14     qDebug()<<"constructor2:"<<this;15 }

 1 #include "testconstructor.h" 2 #include <QDebug> 3  4 int main(int argc, char *argv[]) 5 { 6     TestConstructor *t = new TestConstructor(); 7     qDebug()<<t->value; 8     qDebug()<<t; 9     delete t;10 }

The code execution result is:

Constructor2: 0x22fcf0

Constructor1: 0xdadfb0

15574896

0xdadfb0

On the one hand, the value set for value does not take effect. On the other hand, two constructors create two different objects, which means C ++ cannot call each other like java.

Solution:

Most constructors need to call each other with default parameters. In the C ++ function declaration, you can directly set default parameters (java does not support default parameters ), in this way, you do not need to overload the constructor:

TestConstructor(int value = 10);