xxxx没有命名C ++类型

Question

我是C / C ++的新手，正在尝试提高编码技能。 我正在编写一个最小的代码来计算在大学学习中使用的公式。 此代码包含许多类。 当我尝试构建它时，我在类标题中得到了错误提示。 这是我的代码：

materials.hpp

#ifndef MATERIALS_HPP
#define MATERIALS_HPP

#include <cmath>
#include <iostream>

using namespace std;

class materials{
public: 
double MassNumber, AtomNumber, Density, I, C, a, m, X1, X0, X, delta; 

    materials();
    materials(double, double, double, double, double, double, double, double, double);
     ~materials();
};

materials Magnesium;
materials Cupper;
materials Alluminium;
materials Plumbo;
materials Water;

#endif // MATERIALS_HPP

这就是来源；

materials.cpp

#include "materials.hpp"
#include <cmath>
#include <iostream>

using namespace std;

materials::materials()
{
    MassNumber = AtomNumber = Density = I = a = m = C = X1 = X0 = X = delta = 0.0;
}

materials::materials(double a1, double a2, double a3, double a4, double a5, double a6,double a7, double a8, double a9)
{
    MassNumber = a1;
    AtomNumber = a2;
    Density = a3;
    I = a4;
    C = a5;
    a = a6;
    m = a7;
    X1 = a8;
    X0 = a9;
}

Magnesium.materials(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499);
Cupper.materials(63.0, 29.0, 8.96, 322.0, -4.42, 0.1434, 2.90, 3.28, 0.0254);
Alluminium.materials(26.0, 13.0, 2.70, 166.0, -4.24, 0.0802, 3.63, 3.01, 0.1708);
Plumbo.materials(207.0, 82.0, 11.34, 823.0, -6.20, 0.0936, 3.16, 3.81, 0.3776);
Water.materials(18.0, 10.0, 1.0, 75.0, -3.50, 0.0911, 3.48, 2.80, 0.2400);

还有我遇到的错误；

materials.cpp:64:1: error: 'Magnesium' does not name a type
 Magnesium.materials(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499
);
 ^
materials.cpp:66:1: error: 'Cupper' does not name a type
Cupper.materials(63.0, 29.0, 8.96, 322.0, -4.42, 0.1434, 2.90, 3.28, 0.0254);
^
materials.cpp:68:1: error: 'Alluminium' does not name a type
Alluminium.materials(26.0, 13.0, 2.70, 166.0, -4.24, 0.0802, 3.63, 3.01, 0.1708
);
^
materials.cpp:70:1: error: 'Plumbo' does not name a type
Plumbo.materials(207.0, 82.0, 11.34, 823.0, -6.20, 0.0936, 3.16, 3.81, 0.3776);

^
materials.cpp:72:1: error: 'Water' does not name a type
Water.materials(18.0, 10.0, 1.0, 75.0, -3.50, 0.0911, 3.48, 2.80, 0.2400);
^
make: *** [materials.o] Error 1

我正在Linux上的GCC 4.9.0和Windows上的GCC 4.8.1上使用MinGW进行尝试。 我读过其他有关它的文章，但我做不到。 为什么会出现此错误？

Answer 1

您可能应该对C ++中的类如何工作进行深入的介绍。

问题是，您试图通过先声明一些奇怪的两部分构造

materials Magnesium;

然后尝试显式调用

Magnesium.materials(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499);

但是构造函数在C ++中不能像这样工作！

您应该这样做：

materials Magnesium(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499);

这实际上不是解释类构造细节的地方，但是我可以肯定地说，您应该对此做更多的研究。

Answer 2

如果希望这些全局变量可在其他源文件中访问：

在头文件中更改为：

extern materials Magnesium;
extern materials Cupper;
extern materials Alluminium;
extern materials Plumbo;
extern materials Water;

在源文件中更改为：

materials Magnesium(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499);
materials Cupper(63.0, 29.0, 8.96, 322.0, -4.42, 0.1434, 2.90, 3.28, 0.0254);
materials Alluminium(26.0, 13.0, 2.70, 166.0, -4.24, 0.0802, 3.63, 3.01, 0.1708);
materials Plumbo(207.0, 82.0, 11.34, 823.0, -6.20, 0.0936, 3.16, 3.81, 0.3776);
materials Water(18.0, 10.0, 1.0, 75.0, -3.50, 0.0911, 3.48, 2.80, 0.2400);

---

如果您不希望在其他源文件中访问这些全局变量：

从头文件中删除它：

materials Magnesium;
materials Cupper;
materials Alluminium;
materials Plumbo;
materials Water;

在源文件中更改为：

static materials Magnesium(23.0, 12.0, 1.738, 156.0, -4.53, 0.0816, 3.62, 3.07, 0.1499);
static materials Cupper(63.0, 29.0, 8.96, 322.0, -4.42, 0.1434, 2.90, 3.28, 0.0254);
static materials Alluminium(26.0, 13.0, 2.70, 166.0, -4.24, 0.0802, 3.63, 3.01, 0.1708);
static materials Plumbo(207.0, 82.0, 11.34, 823.0, -6.20, 0.0936, 3.16, 3.81, 0.3776);
static materials Water(18.0, 10.0, 1.0, 75.0, -3.50, 0.0911, 3.48, 2.80, 0.2400);