C++ const的錯誤

bool check_integrity(int pos) const 
    { 
     if ((pos <= 0) || (pos > max_seq) || (pos >= _length + _beg_pos)) 
     { 
      cerr << "!! invalid position: " << pos 
        << " Cannot honor request\n"; 
      return false; 
     } 

     if (_isa == ns_unset) 
     { 
      cerr << "!! object is not set to a sequence." 
        << " Please set_sequence() and try again!\n"; 
      return false; 
     } 

     if (pos > _elem->size()){ 
      cout << "check_integrity: calculating " 
        << pos - _elem->size() << " additional elements\n"; 
      (this->*_pmf)(pos); 
     } 

     return true; 
    } 


    public: 
     typedef void (num_sequence::*PtrType)(int); 
    private: 
     PtrType _pmf;

The above code clip is part of class "num_sequence". I got an error for the following line:C++ const的錯誤

(this->*_pmf)(pos);

The error is: 'const num_sequence *const this' Error: the object has type qualifiers that are not compatible with the member function

謝謝！

來源

2012-08-10 Fihop

您正在試圖調用由指向非const成員函數_pmf對於恆定對象*this。這違反了const-correctness規則。

無論是宣佈你PtrType作爲

typedef void (num_sequence::*PtrType)(int) const;

從 check_integrity功能

bool check_integrity(int pos) 
{ 
    ...

非此即彼

或刪除const。您沒有提供足夠的信息讓其他人決定在這種情況下應該做哪些事情。

來源

2012-08-10 05:43:34 AnT

check_integrity是const功能，所以功能調用也必須const，因此調用PtrType功能也必須是const。

試試這個：

typedef void (num_sequence::*PtrType)(int) const;

注：我沒編譯這個:)只是想大聲。

來源

2012-08-10 05:19:19

您需要更改

typedef void (num_sequence::*PtrType)(int);

到

typedef void (num_sequence::*PtrType)(int) const;

，因爲你是從const函數調用函數

來源

2012-08-10 05:21:53 GradGuy

C++ const的錯誤

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