How to create a static constant member std::string array?

Question

I cannot believe that something that sounds so simple can be so hard.

class OutputHandler {
private:
    static std::string const errorPrefixes[] = {"INFO", "WARNING", "ERROR", "CRASH"};
};

How do I do this properly? From various documentations I understand that I cannot initialize Static Member Objects, regardless of them being constant.

Kerrek SB · Accepted Answer · 2013-10-06 13:35:50Z

3

Write the initialization outside the class, together with the definition:

class OutputHandler
{
private:
    static std::string const errorPrefixes[];
};

std::string const OutputHandler::errorPrefixes[] = {"INFO", "WARNING", "ERROR", "CRASH"};

(The definition is of course subject to the one-definition-rule and must only appear in one single translation unit, e.g. OutputHandler.cpp.)

answered Oct 6, 2013 at 13:35

Kerrek SB

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6 Comments

Jeroen Over a year ago

This is literally the only way to do it? (Like it cannot be done automatically when loading the application without any code outside the class definition? )

Kerrek SB Over a year ago

@Binero: every object (which is odr-used) must be defined. There's no way around that.

Kerrek SB Over a year ago

@Binero: Why don't you have an array of const char * instead?

Jeroen Over a year ago

Because error: in-class initialization of static data member 'const char* OutputHandler::errorPrefixes []' of incomplete type Code: static char const* errorPrefixes[] = {"INFO", "WARNING", "ERROR", "CRASH"};

Jeroen Over a year ago

This did it for me. Thanks static constexpr char const * const arr[] = {"INFO", "WARNING", "ERROR", "CRASH"};

|

Pierre Fourgeaud · Accepted Answer · 2013-10-06 13:37:38Z

3

You have to initialize your static members in a source file to satisfy the one-definition-rule:

// in .h
class OutputHandler {
private:
    static std::string const errorPrefixes[]; // declaration
};

// in .cpp
// definition
std::string const OutputHandler::errorPrefixes[] = {"INFO", "WARNING", "ERROR", "CRASH"};

answered Oct 6, 2013 at 13:37

Pierre Fourgeaud

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