C++ C++；类中没有构造函数的非静态常量成员

我不断地发现这个错误：

警告：非静态常量成员'const char sict:：Weather:：_date[7]' 在没有构造函数的类中[-Wuninitialized]

我不明白

main.cpp 我的编译错误如下

Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
Weather.cpp:11:7: error: ‘weather’ has not been declared
Weather.cpp: In function ‘void sict::set(const char**, double, double)’:
Weather.cpp:12:11: error: ‘_date’ was not declared in this scope
Weather.cpp:12:18: error: ‘date_description’ was not declared in this scope
Weather.cpp:13:11: error: ‘high’ was not declared in this scope
Weather.cpp:14:10: error: ‘low’ was not declared in this scope
Weather.cpp: At global scope:
Weather.cpp:18:7: error: ‘weather’ has not been declared
Weather.cpp:18:26: error: non-member function ‘void sict::display()’ cannot have cv-qualifier
Weather.cpp: In function ‘void sict::display()’:
Weather.cpp:19:57: error: ‘_date’ was not declared in this scope
Weather.cpp:19:86: error: ‘_high’ was not declared in this scope
Weather.cpp:19:95: error: ‘_low’ was not declared in this scope
Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
In file included from w3_in_lab.cpp:15:0:
Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
w3_in_lab.cpp: In function ‘int sict::main()’:
w3_in_lab.cpp:29:27: error: no matching function for call to ‘sict::Weather::Weather(int&)’
w3_in_lab.cpp:29:27: note: candidates are:
Weather.h:8:8: note: sict::Weather::Weather()
Weather.h:8:8: note:   candidate expects 0 arguments, 1 provided
Weather.h:8:8: note: sict::Weather::Weather(const sict::Weather&)
Weather.h:8:8: note:   no known conversion for argument 1 from ‘int’ to ‘const sict::Weather&’

---

编译器告诉您类中有一个

const

成员。作为

const

，它的值只能在类构造函数中设置（然后再也不能更改）

---

但是该类没有构造函数，因此永远不会设置值。

您的类中有一个const成员

Weather

。在C++中，非静态成员只能在构造函数初始化列表中初始化（参见）。 要解决此问题，您可以：

• 将_数据成员声明为

  静态

  ，这样可以初始化它
• 为类声明并定义构造函数，并在其中初始化数据

否则，成员

\u data

永远不会初始化，因此无法使用其值

如果您至少使用C++11，还可以在类定义中初始化非静态成员：

class Weather{
    const char _date[7] = "mydate";
}

• 您应该在定义之前声明类。这就是为什么会出现编译错误
• 不要在setter中更新const

---

“作为常量，它的值只能在类构造函数中设置（然后永不更改）。”它也可以在类定义

const char something[]={…}中初始化
#ifndef SICT_WEATHER_H_
#define SICT_WEATHER_H_

namespace sict{
class Weather{
    const char _date[7];
    double _high;
    double _low;

public:
    void set(const char* _date[7], double _high, double _low);
    void display() const;

};
}
#endif

Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
Weather.cpp:11:7: error: ‘weather’ has not been declared
Weather.cpp: In function ‘void sict::set(const char**, double, double)’:
Weather.cpp:12:11: error: ‘_date’ was not declared in this scope
Weather.cpp:12:18: error: ‘date_description’ was not declared in this scope
Weather.cpp:13:11: error: ‘high’ was not declared in this scope
Weather.cpp:14:10: error: ‘low’ was not declared in this scope
Weather.cpp: At global scope:
Weather.cpp:18:7: error: ‘weather’ has not been declared
Weather.cpp:18:26: error: non-member function ‘void sict::display()’ cannot have cv-qualifier
Weather.cpp: In function ‘void sict::display()’:
Weather.cpp:19:57: error: ‘_date’ was not declared in this scope
Weather.cpp:19:86: error: ‘_high’ was not declared in this scope
Weather.cpp:19:95: error: ‘_low’ was not declared in this scope
Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
In file included from w3_in_lab.cpp:15:0:
Weather.h:10:21: warning: non-static const member ‘const char sict::Weather::_date [7]’ in class without a constructor [-Wuninitialized]
w3_in_lab.cpp: In function ‘int sict::main()’:
w3_in_lab.cpp:29:27: error: no matching function for call to ‘sict::Weather::Weather(int&)’
w3_in_lab.cpp:29:27: note: candidates are:
Weather.h:8:8: note: sict::Weather::Weather()
Weather.h:8:8: note:   candidate expects 0 arguments, 1 provided
Weather.h:8:8: note: sict::Weather::Weather(const sict::Weather&)
Weather.h:8:8: note:   no known conversion for argument 1 from ‘int’ to ‘const sict::Weather&’

class Weather{
    const char _date[7] = "mydate";
}