如何在 C++ 中提供实现？ [关闭]答案

【问题标题】：How to provide an Implementation in c++? [closed]如何在 C++ 中提供实现？ [关闭]
【发布时间】：2014-11-03 23:26:26
【问题描述】：

往年考试2出现以下问题。

class SchoolBus
{
public:
    SchoolBus(int seats, int seatedStudents);
    bool addStudents(int students);
    bool removeStudents(int students);
    int getStudents() const;

private:
    int seats;
    int seatedStudents;
};

2) 提供 SchoolBus 构造函数的实现。

SchoolBus(int seats, int seatedStudents) {
   this->seats = seats;
   this->seatedStudents = seatedStudents;
}

我没有得到 #2。我知道这就是答案，但是您将如何在代码中编写并编译它？我想实际编译它，看看它是如何工作的。

【问题讨论】：

你试过编译代码吗？

标签： c++ class implementation

【解决方案1】：

在#2 中，代码称为构造函数，因此我将使用我更熟悉的术语来编写构造函数：

SchoolBus::SchoolBus(int seating_capacity, int students_in_bus)
: seats(seating_capacity),
  seatedStudents(students_in_bus)
{
}

要对其进行编码，我可能会将其放入一个名为“school_bus.cpp”的文件中：

#include "school_bus.hpp"

SchoolBus::SchoolBus(int seating_capacity, int students_in_bus)
: seats(seating_capacity),
  seatedStudents(students_in_bus)
{
}

我会将类声明放在一个名为“school_bus.hpp”的头文件中：

class SchoolBus
{
public:
    SchoolBus(int seats, int seatedStudents);
    bool addStudents(int students);
    bool removeStudents(int students);
    int getStudents() const;

private:
    int seats;
    int seatedStudents;
};

要编译，我可能会使用g++：

  g++ -g -o school_bus.o -c school_bus.cpp

为了测试它，我会创建一个“main”函数：

#include "school_bus.hpp"
int main(void)
{
  static SchoolBus yellow_bus(25, 36);
  return 0;
}

这可能需要构建和链接：

g++ -g -o school_bus.exe main.cpp school_bus.o

然后我可以使用调试器：

gdb ./school_bus.exe

【讨论】：

【解决方案2】：

构造函数实现没有正确限定。它应该以类名作为前缀。

这个：

SchoolBus(int seats, int seatedStudents) {
   this->seats = seats;
   this->seatedStudents = seatedStudents;
}

应该变成：

SchoolBus::SchoolBus(int seats, int seatedStudents) {
   this->seats = seats;
   this->seatedStudents = seatedStudents;
}

那么它应该可以工作了。

【讨论】：

【解决方案3】：

要么像这样完整地声明：

class SchoolBus
{
public:
    SchoolBus(int seats, int seatedStudents)
    {
        this->seats = seats;
        this->seatedStudents = seatedStudents;
    }
    bool addStudents(int students);
    bool removeStudents(int students);
    int getStudents() const;

private:
    int seats;
    int seatedStudents;
};

或将两者分开

//in schoolbus.h
#pragma once
class SchoolBus
{
public:
    SchoolBus(int seats, int seatedStudents);
    bool addStudents(int students);
    bool removeStudents(int students);
    int getStudents() const;

private:
    int seats;
    int seatedStudents;
};

//in schoolbus.cpp
#include "schoolbus.h"

SchoolBus::SchoolBus(int seats, int seatedStudents) {
   this->seats = seats;
   this->seatedStudents = seatedStudents;
}

还值得注意的是，通常这会在初始化列表中完成，如下所示：

SchoolBus::SchoolBus(int pSeats, int pSeatedStudents) :
  seats(pSeats),
  seatedStudents(pSeatedStudents)
{
}

【讨论】：