can't access const static std::map enum struct

Question

I am trying to have a enum struct mapping to guarante a default value to a config value if it does not exsist and to guarante only access to "real" config values.(No std::string get)

So the Header looks like this:

enum ConfigValues
{
    LOG_LEVEL,
};

class Config
{
public:
    std::string get(const ConfigValues& key);
private:
    struct ConfigMapping
    {
        std::string configKeyString;
        std::string defaultValue;
    };

    const static std::map<ConfigValues, ConfigMapping> m_mapping;
}

And the cpp contains this:

const std::map<ConfigValues, Config::ConfigMapping> Config::m_mapping=
{
    {LOG_LEVEL, { "logLevel", "5" } },
};
std::string Config::get(const ConfigValues& key)
{
    std::string key = m_mapping[key].configKeyString; // <-- Does not work
}

But i cant access the map.

In Config::get(), both parameter and local are named key. Is that a typo in the example code or the actual problem? Maybe the actual compiler message might make things clearer. — stefaanv
– stefaanv, Commented Jul 28, 2015 at 8:09
See also stackoverflow.com/questions/5134614/c-const-map-element-access — stefaanv
– stefaanv, Commented Jul 28, 2015 at 8:21

Telokis · Accepted Answer · 2015-07-28 08:10:41Z

6

operator[] is not const for a std::map.

Use at instead.

Before C++11 :

If you are not using C++11, you have to use find which has a const version.

edited Jul 28, 2015 at 8:10

answered Jul 28, 2015 at 7:58

Telokis

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2 Comments

bemeyer Over a year ago

Ah right. Didn't see that. going to accept this in some minutes when it's enabled. Thanks for that hint.

Telokis Over a year ago

I just updated my answer for people looking for the non-C++11 answer.

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