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我有一个基类，代表一些（通用）硬件的处理程序，特定实例从中派生。处理程序接收的命令协议包括一个字符串，该字符串确定处理程序执行的功能。

我想使用构造字符串到函数指针的静态映射HashMap（据我所知，这基本上类似于std::map，所以这应该或多或少地适用于 JUCE 和std）。我希望它是静态的，因为这个映射不会改变，而且我不想在每次实例化处理程序时都重新构建它（这可能会发生很多）。

//general hardware handler
class HandlerBase {
public:

    // all command handlers take a BazCommand reference and return success
    typedef bool (HandlerBase::* commandHandler)(BazCommand&);

    // this is the mapping of String to the handler function that
    // determines which function to run when getting a command
    typedef HashMap<String, commandHandler> CmdList;
}

// handler for the Foomatic Barrifier 2000
class FoomaticHandler : public HandlerBase {
public:

    //one of the Foomatic handler functions
    bool barrify(BazCommand& cmd) {
        return true;
    }

    static CmdList createCmdMapping() {
        CmdList l;

        l.set("bar", (commandHandler) &FoomaticHandler::barrify);
        // add all Foomatic handler functions here

        return l;
    }

    bool doCommand(BazCommand& cmd) {
        String cmdString = cmd.getCmdString();

        //execute correct function here
    }

    //this cmdList is static and shared betweeen all Foomatic handlers
    static CmdList cmdList;
}

// set up the Foomatic command hashmap
FoomaticHandler::CmdList FoomaticHandler::cmdList =
        FoomaticHandler::createCmdMapping();

但是，这种方法会产生很多错误。我尝试了几种替代安排。这个特定的产生：

../core/../../../juce/JuceLibraryCode/modules/juce_audio_basics/../juce_core/containers/juce_HashMap.h: In static member function ‘static HandlerBase::CmdList FoomaticHandler::createCmdMapping()’:
 ../core/../../../juce/JuceLibraryCode/modules/juce_audio_basics/../juce_core/containers/juce_HashMap.h:445:5: error: ‘juce::HashMap<KeyType, ValueType, HashFunctionToUse, TypeOfCriticalSectionToUse>::HashMap(const juce::HashMap<KeyType, ValueType, HashFunctionToUse, TypeOfCriticalSectionToUse>&) [with KeyType = juce::String, ValueType = bool (HandlerBase::*)(BazCommand&), HashFunctionToUse = juce::DefaultHashFunctions, TypeOfCriticalSectionToUse = juce::DummyCriticalSection, juce::HashMap<KeyType, ValueType, HashFunctionToUse, TypeOfCriticalSectionToUse> = juce::HashMap<juce::String, bool (HandlerBase::*)(BazCommand&)>]’ is private
 FoomaticHandler.cpp:77:16: error: within this context

创建这样的静态字符串-> 成员函数映射的正确方法是什么？并且可以将createCmdList()其制成纯虚拟来强制实施吗？

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