unordered_map inside C++ class

August 10, 2022

I am writing a simple logging class with C++. I want to create an unordered_map to store logging_levels, but compiling fails.

#include <iostream>
#include <unordered_map>
#include <string>

class logging {
public:
    std::unordered_map<std::string, int> m_log_levels;
    m_log_levels["info"] = 2;
    m_log_levels["warning"] = 1;
    m_log_levels["error"] = 0;
private:
    int m_level = m_log_levels["info"];
public:
    void setLevel(int level) {
        m_level = level;
    }
    void warn(const char* message) {
        std::cout << message << std::endl;
    }
};

>Solution :

You can’t put arbitrary code wherever you want in a class definition.

Initialize the hash table in a constructor i.e.

class logging {
public:
    std::unordered_map<std::string, int> m_log_levels;
private:
    int m_level;
public:
    logging() { // <<< this is a constructor...
        m_log_levels["info"] = 2;
        m_log_levels["warning"] = 1;
        m_log_levels["error"] = 0;
        m_level = m_log_levels["info"];
    }

    void setLevel(int level) {
        m_level = level;
    }
    void warn(const char* message) {
        std::cout << message << std::endl;
    }
};