C++ – error: invalid in-class initialization of static data member of non-integral type ‘const char[]’

I'm getting tons of errors on my private class members. Please help me work through them.

error: a brace-enclosed initializer is not allowed here before '{' token

error: invalid in-class initialization of static data member of non-integral type 'const char []'

error: 'LETTERS_ARR' has not been declared

error: expected ',' or '…' before '+' token

error: ISO C++ forbids initialization of member 'SNTNC_SMLRTY_THRSHLD_DEFAULT'

error: making 'SNTNC_SMLRTY_THRSHLD_DEFAULT' static**

private:
    std::vector<std::string> files_vec; 
    std::vector<std::string> get_file_sntncs(std::fstream&);
    std::vector<std::string> get_sntnc_wrds(const std::string&);
    double sntnc_smlrty_qtnt(std::vector<std::string>, std::vector<std::string>);
    static const char LETTERS_ARR[] = {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'."};
    static const std::set<char> LETTERS_SET(LETTERS_ARR, LETTERS_ARR + sizeof(LETTERS_ARR)/sizeof(char));
    double sntnc_smlrty_thrshld; 
    static const double SNTNC_SMLRTY_THRSHLD_DEFAULT = 0.5;

Best Answer

In C++ you are not allowed to supply in-class initializers for static members of non-integral non-enum type. For such members the initializer is supplied at the point of definition, not at the point of declaration.

Alternatively, as @juanchopanza noted in the comments, you can declare your static members as constexpr instead of const (assuming you are using a C++11 compiler), which will permit you to supply in-class initializers for such members just like you do in your original code.

Related Solutions

C++ – error: request for member ‘..’ in ‘..’ which is of non-class type

Foo foo2();

change to

Foo foo2;

You get the error because compiler thinks of

Foo foo2()

as of function declaration with name 'foo2' and the return type 'Foo'.

But in that case If we change to Foo foo2 , the compiler might show the error " call of overloaded ‘Foo()’ is ambiguous".

C++ – Static constant string (class member)

You have to define your static member outside the class definition and provide the initializer there.

First

// In a header file (if it is in a header file in your case)
class A {   
private:      
  static const string RECTANGLE;
};

and then

// In one of the implementation files
const string A::RECTANGLE = "rectangle";

The syntax you were originally trying to use (initializer inside class definition) is only allowed with integral and enum types.

Starting from C++17 you have another option, which is quite similar to your original declaration: inline variables

// In a header file (if it is in a header file in your case)
class A {   
private:      
  inline static const string RECTANGLE = "rectangle";
};

No additional definition is needed.

Starting from C++20 instead of const you can declare it constexpr in this variant. Explicit inline would no longer be necessary, since constexpr implies inline.

Best Answer

Related Solutions

C++ – error: request for member ‘..’ in ‘..’ which is of non-class type

C++ – Static constant string (class member)

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