C++ - 模板类的拷贝构造函数

Question

我的班级是由出向量的向量的矩阵，我似乎已经在我的构造问题：

 #include <vector> 
     #include <exception> 
     #include <iostream> 

     using namespace std; 

     template<class T> 
     class Matrix 
     { 
     private: 

     unsigned int _rows; 
     unsigned int _cols; 
     vector <vector<T>> _matrix; 

    public: 

     const unsigned int INITIAL_ROW_SIZE = 1; 
     const unsigned int INITIAL_COL_SIZE = 1; 

     Matrix() : _rows(INITIAL_COL_SIZE), _cols(INITIAL_COL_SIZE), 
        _matrix(1,vector<T>(1)) { 
      cout << "ctor" << endl; 
     } 

     Matrix (unsigned int rows, unsigned int cols) : _rows(rows), _cols(cols),_matrix(_rows,vector<T>(_cols)  { 
     } 

    Matrix (const Matrix<T> &other) :Matrix(other._rows, other._cols) 
    { 
     for(int i = 0; i < _rows; i++) 
     { 
      copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i]); 
     } 
     }; 
    } 

当我尝试使用的代码将无法编译拷贝构造函数， 在Matric<int> m(5,5); Matrix<int> n=(m);因为：

 In file included from /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/vector:60:0, 
        from /cppex3/ex3/Matrix.hpp:8, 
        from /cppex3/ex3/Tester.cpp:6: 
    /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h: In instantiation of '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = const std::vector<int, std::allocator<int> >*; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]': 
    /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:438:45: required from '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false; _II = __gnu_cxx::__normal_iterator<const std::vector<int, std::allocator<int> >*, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]' 
    /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:471:8: required from '_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const std::vector<int, std::allocator<int> >*, std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >; _OI = std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > >]' 
    /ex3/Matrix.hpp:42:13: required from 'Matrix<T>::Matrix(const Matrix<T>&) [with T = int]' 
    /ex3/Tester.cpp:25:20: required from here 
    /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:394:57: error: no type named 'value_type' in '[01mstruct std::iterator_traits<std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >' 
      typedef typename iterator_traits<_OI>::value_type _ValueTypeO; 
                  ^
    /usr/lib/gcc/x86_64-pc-cygwin/5.4.0/include/c++/bits/stl_algobase.h:399:9: error: no type named 'value_type' in 'struct std::iterator_traits<std::vector<std::vector<int, std::allocator<int> >, std::allocator<std::vector<int, std::allocator<int> > > > >' 
      && __are_same<_ValueTypeI, _ValueTypeO>::__value); 
      ^

我怀疑我的_Matrix应留作成员的initalization是不正确的，但我不知道。它也可以通过std :: copy但语法看起来正确。

Answer 1

与

copy(other._matrix[i].begin(), other._matrix[i].end(), 
    std::back_inserter(_matrix[i])); 

或

Matrix (const Matrix<T> &other) 
    : _rows{other._rows}, _cols{other._cols}, _matrix{other._matrix} 
{ 
} 

Answer 2

试用试用此代码，它的工作原理

更换你

copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i]); 

与

copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i].begin()); 

下面是完整的代码。

#include <vector> 
#include <exception> 
#include <iostream> 

using namespace std; 

template<class T> 
class Matrix 
{ 
private: 

    unsigned int _rows; 
    unsigned int _cols; 
    vector <vector<T> > _matrix; 

public: 

    Matrix() : _rows(1), _cols(1), 
       _matrix(1,vector<T>(1)) 
    { 
     cout << "ctor" << endl; 
    } 

    Matrix (unsigned int rows, unsigned int cols) : _rows(rows), _cols(cols) 
    { 
     _matrix=vector< vector<T> >(rows,vector<T>(cols)); 
    } 


    Matrix (const Matrix<T> &other) 
    : _rows{other._rows}, _cols{other._cols}, _matrix{other._matrix} 
    { 
     for(int i = 0; i < _rows; i++) 
     { 
      std::copy(other._matrix[i].begin(), other._matrix[i].end(), _matrix[i].begin()); 
     } 
    } 

}; 


int main(int argc, char const *argv[]) 
{ 
    Matrix<int> m(5,5); 
    Matrix<int> n1(m); 
    Matrix<int> n2(m); 
    return 0; 
} 

另外

Matrix (const Matrix<T> &other) :Matrix(other._rows, other._cols); 

与

Matrix (const Matrix<T> &other) { 
    Matrix(other._rows, other._cols); 
...