i18n::strict — a C++ library for strict typed internationalization

A strictly typed, lightweight internationalization and localization system for multilingual programs.

Main features

• Dictionaries are written in code, and the presence and correctness of translations are checked by the compiler
• Built-in support for string formatting based on std::format
• Static verification of the required number of substitutions in the translated strings
• Clean code without singletons and other magic
• Support for dynamic translation switching. This can be useful, for example, in HTTP request handlers
• Support for lazy translation. This allows you to generate a translatable string once, and then, for example, translate it into the system language in the error handler during logging, and return it in the request language in the server response.
• A library with a single header makes it easy to add translations to your project

Requirements and dependencies

• C++20
• No dependencies requires

Examples of usage

#include <i18n_strict.h>

struct test_dict : public i18n_strict::dict {
    str<> app_started;
    str<int, std::string> transfer_money_to_account;
};

test_dict create_en_test_dict()
{
    return {
        .app_started { "Application started" },
        .transfer_money_to_account { "Transfer {} to account {}" },
    };
}

test_dict create_ru_test_dict()
{
    return {
        .app_started { "Приложение запущено" },
        .transfer_money_to_account { "Перевести {} на счет {}" },
    };
}

auto tr = i18n_strict::create_text_translator<test_dict>("ru",
    {
        { "en", create_en_test_dict() },
        { "ru", create_ru_test_dict() },
    });
    
TEST_CASE("Translation")
{
    auto tr = i18n_strict::create_text_translator<test_dict>("ru",
        {
            { "en", create_en_test_dict() },
            { "ru", create_ru_test_dict() },
        });

    SECTION("Translate simple text to english")
    {
        REQUIRE(tr->translate("en", &test_dict::app_started) == "Application started");
    }
    SECTION("Translate simple text to default language")
    {
        REQUIRE(tr->translate(&test_dict::app_started) == "Приложение запущено");
    }
    SECTION("Translate formatted message to english")
    {
        REQUIRE(tr->translate("en", &test_dict::transfer_money_to_account, 10, std::string("John"))
            == "Transfer 10 to account John");
    }
    SECTION("Use translatable string to translate later")
    {
        i18n_strict::tr_str str(tr, &test_dict::transfer_money_to_account, 10, "John");
        REQUIRE(str.translate("en") == "Transfer 10 to account John");
        REQUIRE(str.translate() == "Перевести 10 на счет John");
    }
}

Installation

Just copy and include lib/i18n_strict.h in your project.

Include with CMake FetchContent

Add to your cmake project:

# Use C++20
set(CMAKE_CXX_STANDARD 20)

# Include i18n::strict
include(FetchContent)
FetchContent_Declare(
  i18n_strict
  GIT_REPOSITORY https://github.com/navrocky/i18n-strict.git
  GIT_TAG        1.0.0 # Place the needed version here
  OVERRIDE_FIND_PACKAGE
)
set(BUILD_TESTS OFF CACHE BOOL "Disable tests" FORCE)
FetchContent_MakeAvailable(i18n_strict)
include_directories(${i18n_strict_SOURCE_DIR}/lib)

After then include library as usual:

#include <i18n_strict.h>

Backlog

• Run unit tests with Github Actions
• Improve inline documentation
• Generate documentation with Doxygen
• Describe installation with CMake FetchContent
• Add package to vcpkg
• Add package to Conan Center