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使用QT_TR_NOOP宏，看例子

QString getText(OperationStateEnum state)
{
    static std::map<OperationStateEnum, const char*> data =
    {
        {OperationStateEnum::UNKNOW, QT_TR_NOOP("未知")},
        {OperationStateEnum::NOSAVE, QT_TR_NOOP("未保存")},
        {OperationStateEnum::SAVED, QT_TR_NOOP("已保存")}
    };

    auto iter = data.find(state);
    if ( iter != data.end())
    {
        return tr(iter->second);
    }

    return "";
}

QT_TR_NOOP，NOOP是 No Operation 的缩写，意为 “无操作”，原型如下

#define QT_TR_NOOP(sourceText) (sourceText)

展开后就是原样返回输入的字符串，运行时不做任何操作（不翻译、不转换、不分配内存）。它存在的唯一目的就是标记：告诉 lupdate 工具（Qt 的翻译提取工具）这个字符串需要被提取到翻译文件（.ts）中。有些字符串需要存储在静态数据结构中（如 static const char* 数组、std::map），为了提高效率等原因，因此不能直接调用 tr()（否则会在程序启动时固定翻译，无法动态切换语言）。QT_TR_NOOP 让你先标记这些字符串，等到真正使用时再调用 tr() 来翻译，从而既支持 lupdate 提取，又支持运行时动态切换语言。

官方说明：

QT_TR_NOOP(sourceText)
Marks the UTF-8 encoded string literal sourceText for delayed translation in the current context (class).
The macro tells lupdate to collect the string, and expands to sourceText itself.
Example:
QString FriendlyConversation::greeting(int type)
{
static const char *greeting_strings[] = {
QT_TR_NOOP("Hello"),
QT_TR_NOOP("Goodbye")
};
return tr(greeting_strings[type]);
}

The macro QT_TR_NOOP_UTF8() is identical and obsolete; this applies to all other _UTF8 macros as well.