Question

我想创建一个类，这些类是从使用程序的某个特征时派生出来的，只需要初始化一次。
我使用静态bool成员和默认构造函数创建了类。默认构造函数检查静态成员并在需要时运行初始化：

class WireUser {
public:
    static bool wireIntialized;
    WireUser::WireUser();
};

bool WireUser::wireInitialized = false;

WireUser::WireUser() {
    if (!wireInitialized) {
        Wire.begin();
        wireInitialized = true;
    }
};

当我尝试编译时，我收到以下错误：

 error: 'bool WireUser::wireInitialized' is not a static member of 'class WireUser'
 bool WireUser::wireInitialized = false;

如果删除该行，则该成员初始化为false，包含if (!wireInitialized) {的行上会出现相同的错误

我不明白我做错了什么。

Answer 1

您的代码中存在许多拼写错误和小错误/警告（注释中说明的修复步骤）：

class WireUser {
public:
  static bool wireInitialized;
  WireUser(); // Don't use scope specifiers in declarations:  WireUser::WireUser();
};

bool WireUser::wireInitialized = false; // Typo fixed here 'wireInitialized' isn't the 
                                        // same as         'wireIntialized'

WireUser::WireUser() {
  if (!wireInitialized) {
    // Wire.begin(); Commented out because it's not in context of your question
    wireInitialized = true;
  }
} //; <<<< Omit the semicolon to get rid of the warning

int main (){
    WireUser wu;
    return 0;
}

Live Demo

此外，您应该考虑使该线程安全地进行初始化 std::atomic<bool>可能是正确的选择：

#include <atomic>

class WireUser {
public:
  static std::atomic<bool> wireInitialized;
  WireUser();
};

std::atomic<bool> WireUser::wireInitialized = {false};

WireUser::WireUser() {
  if (!wireInitialized.exchange(true)) {
    // Wire.begin();
    // wireInitialized = true;
  }
}

int main (){
    WireUser wu;
    return 0;
}

Live Demo

引用类的静态成员结果＆＃34;不是类的静态成员＆＃34;

1 个答案: