c++ - std::map::iterator references non-existing object? -

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निम्न कोड को ध्यान में रखते हुए: 

  वर्ग MyClass {सार्वजनिक: int someInt; मायक्लास (): कुछ इंट (666) {}}; Int main () {std :: map & lt; int, MyClass & gt; myMap; Std :: map & lt; int, MyClass & gt; :: iterator = myMap.end (); कॉन्स्ट मायक्लास & amp; रेफरी = यह- & gt; दूसरा; Std :: cout & lt; & lt; Ref.someInt & lt; & lt; std :: endl; }   
 चूंकि नक्शा खाली है और  यह = myMap.end () , क्या वस्तु  it-> second  संदर्भ करता है? क्या यह एक अमान्य संदर्भ है क्योंकि  यह = myMap.end () ?  
  मानचित्र & lt; int, MyClass & gt;   का एक उदाहरण नहीं बनाता है MyClass ।   
 
 
 
 वस्तु क्या  it-> दूसरा < / कोड> संदर्भ? क्या यह एक अमान्य संदर्भ है क्योंकि  यह = myMap.end () ?   
 वास्तव में  myMap.end ()  एक वैध इटरेटर है लेकिन यह dereferenced नहीं होना चाहिए।  यह-> दूसरा  सही ढंग से करने का प्रयास करता है और अपरिभाषित व्यवहार का कारण बनता है।  
 
  मानचित्र & lt; int, MyClass & gt;  एक उदाहरण MyClass का।   
 यह सच है, लेकिन अप्रासंगिक  myMap.end ()  हमेशा  myMap  â ???? की सामग्री की कोई बात नहीं होगी एक पिछले एक अंत के लिए एक संदर्भ होते हैं ?? इटरेटर, जिसे कभी भी डीरेंस नहीं किया जाना चाहिए।

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