c++ 类的定义和使用

#include "stdafx.h"#include <iostream>#include <string>using namespace std;class A{private:    int n2;    int n1;public:    A() :n2(34), n1(n2+1) {}    void Print() {        cout << "n1:" << n1 << ", n2: " << n2 << endl;    }};int main(){    A a;    a.Print();    getchar();    return 1;}

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对上面代码稍微做调整： 将n1和n2两个变量定义的顺序互换一下

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#include "stdafx.h"#include <iostream>#include <string>using namespace std;class A{private:    int n1;    int n2;public:    A() :n2(34), n1(n2+1) {}    void Print() {        cout << "n1:" << n1 << ", n2: " << n2 << endl;    }};int main(){    A a;    a.Print();    getchar();    return 1;}

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打印结果：

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由此可以总结： 构造函数中，变量初始化的顺序，是以变量定义的顺序来定的，而不是简单的以构造函数中变量出现的顺序来定的

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还可以使用有参的构造函数：

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#include "stdafx.h"#include <iostream>#include <string>using namespace std;class A{private:    int n1;    int n2;public:    A(int k1,int k2) :n2(k1), n1(k2) {}    void Print() {        cout << "n1:" << n1 << ", n2: " << n2 << endl;    }};int main(){    A a(78,97);    a.Print();    getchar();    return 1;}

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打印结果：

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下面对上面进行改造一下：

#include "stdafx.h"#include <iostream>#include <string>using namespace std;class A{private:    int n1;    int n2;public:    A(int k1) :n2(k1), n1(n2) {}    void Print() {        cout << "n1:" << n1 << ", n2: " << n2 << endl;    }};int main(){    A a(115);    a.Print();    getchar();    return 1;}

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打印结果：

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通过最后一个例子，再次证明，变量初始化的顺序是严格按照各个变量定义的先后顺序来的，而不是简单的依据各变量在构造函数中出现的先后顺序来定的

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下面两种写法是一个意思：
写法一：

public:    A(int k1,int k2) {        n1 = k1;        n2 = k2;    }

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写法二：

public:    A(int k1,int k2) :n1(k1),n2(k2){}

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FR:海涛高软（hunk Xu)