[C++知识库]C++中创建对象时三种方式与构造函数

#include <iostream>
using namespace std;

class complax
{
public:
    complax(double r=0,double i=0)
    :re(r),im(i)
    {cout<<"create function with parms"<<endl;}
    double real()const{return re;}
    double imag()const{return im;}
private:
    double re,im;
};

int main() {
    complax c1();
    cout<<"~~~~~~~~"<<endl;
    complax c3;
    cout<<"~!!!!!!!!!"<<endl;
    complax* c2 = new complax();
    return 0;
}

输出：

C:\Users\12431\CLionProjects\untitled\cmake-build-debug\untitled.exe
~~~~~~~~
create function with parms
~!!!!!!!!!
create function with parms

Process finished with exit code 0

?三种构造方式中，第一种方式不会使用显式构造函数（使用隐藏构造函数），其他两种方式都会使用，且当出现歧义构造函数时候，第一种方式不会报错，而其他两种方式会报错，如下：

#include <iostream>
using namespace std;

class complax
{
public:
    complax(double r=0,double i=0)
    :re(r),im(i)
    {
        cout<<"create function with parms"<<endl;
    }
    complax()
    :re(0),im(0)
    {
        cout<<"不带参数的构造函数"<<endl;
    }
    double real()const{return re;}
    double imag()const{return im;}

private:
    double re,im;
};

int main() {
    complax c1();
    cout<<"~~~~~~~~"<<endl;
    complax c3;
    cout<<"~!!!!!!!!!"<<endl;
    complax* c2 = new complax();
    return 0;
}

报错信息为：

?

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