Declaration and definition mismatch

Question

A declaration and definition mismatch in my template class (everything irrelevant has been cut out):

template <typename LanguageMap>
class WidgetLanguageManager
{
    public:
        enum class Language { DE, ENG, PL };
    protected:
        Language language;
        //Some protected fields
    public:
        explicit WidgetLanguageManager(const Language& language);
        explicit WidgetLanguageManager(const QString& language);
        Language ToLanguage(const QString& language);
    protected:
        //some protected methods
};


template <typename LanguageMap>
Language WidgetLanguageManager<LanguageMap>::ToLanguage(const QString& language) // this cannot be matched with a declaration
{
    for (QChar& c: language)
    {
        c = c.toLower();
    }

    switch (language)
    {
        case "german": return Language::DE;
        case "english": return Language::ENG;
        case "polish": return Language::PL;
    }
    throw RuntimeError("Wrong language paremeter.");
}

Please help because I cannot see any reason behind that.

For such questions, always provide the error message(s). – Apr 07 '20 at 07:29 — , Apr 07 '20 at 07:29

NutCracker · Accepted Answer · 2020-04-07T07:25:26.813

2

Following would work:

template <typename LanguageMap>
typename WidgetLanguageManager<LanguageMap>::Language WidgetLanguageManager<LanguageMap>::ToLanguage(const QString& language)
// ^^^^^ 'typename' keyword needed because 'Language' is dependent name

Since enum class Language is part of WidgetLanguageManager template class, you need to precede it with the scope operator.

edited Apr 07 '20 at 07:25

answered Apr 07 '20 at 07:14

NutCracker

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1

This helped: template typename WidgetLanguageManager::Language WidgetLanguageManager::ToLanguage(const QString& language) – slavic-d Apr 07 '20 at 07:24

score 1 · Answer 2 · answered Apr 07 '20 at 07:37

1

Alternatively to extra typename, you might use trailing return type:

template <typename LanguageMap>
auto WidgetLanguageManager<LanguageMap>::ToLanguage(const QString& language)
-> Language
{
/*..*/
}

answered Apr 07 '20 at 07:37

Jarod42

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Declaration and definition mismatch

2 Answers2