问题描述
我正在尝试删除模板类型名称向量的第一个值。使用 vector stl 中的 erase() 方法，我不断收到此错误：
TTrie.inc:56:19: error: passing ‘const std::vector<char,std::allocator<char> >’ as ‘this’ argument discards qualifiers [-fpermissive]
56 | sequence.erase(it);
| ~~~~~~~~~~~~~~^~~~
In file included from /usr/include/c++/10/vector:67,from TTrie.h:5,from TTrieTest.cpp:1:
/usr/include/c++/10/bits/stl_vector.h:1430:7: note: in call to ‘std::vector<_Tp,_Alloc>::iterator std::vector<_Tp,_Alloc>::erase(std::vector<_Tp,_Alloc>::const_iterator) [with _Tp = char; _Alloc = std::allocator<char>; std::vector<_Tp,_Alloc>::iterator = std::vector<char,std::allocator<char> >::iterator; std::vector<_Tp,_Alloc>::const_iterator = std::vector<char,std::allocator<char> >::const_iterator]’
1430 | erase(const_iterator __position)
| ^~~~~
In file included from TTrie.h:115,from TTrieTest.cpp:1:
TTrie.inc: In instantiation of ‘TTrie<DataType>& TTrie<DataType>::operator+=(const std::vector<DataType>&) [with DataType = std::__cxx11::basic_string<char>]’:
TTrieTest.cpp:93:10: required from here
TTrie.inc:56:19: error: passing ‘const std::vector<std::__cxx11::basic_string<char> >’ as ‘this’ argument discards qualifiers [-fpermissive]
56 | sequence.erase(it);
| ~~~~~~~~~~~~~~^~~~
In file included from /usr/include/c++/10/vector:67,_Alloc>::const_iterator) [with _Tp = std::__cxx11::basic_string<char>; _Alloc = std::allocator<std::__cxx11::basic_string<char> >; std::vector<_Tp,_Alloc>::iterator = std::vector<std::__cxx11::basic_string<char> >::iterator; std::vector<_Tp,_Alloc>::const_iterator = std::vector<std::__cxx11::basic_string<char> >::const_iterator]’
1430 | erase(const_iterator __position)
| ^~~~~
In file included from TTrie.h:115,from TTrieTest.cpp:1:
是否有问题，因为序列应该是常量？我是否以某种方式声明迭代器错误？这是我的代码。如果您有任何问题，请告诉我：
template<typename DataType>
TTrie<DataType>& TTrie<DataType>::operator+=(const std::vector<DataType>& sequence) {
const DataType c = sequence[0];
const TTrie<DataType>* child = getChild(c); //Returns a pointer to a child node or a nullptr
if (!child) {
TTrie<DataType>* n = new TTrie<DataType>(c);
edgeMap[c] = n;
}
if(sequence.size() > 1) {
typename std::vector<DataType>::const_iterator it;
it = sequence.cbegin(); //First value of sequence
sequence.erase(it);
*edgeMap[c] += sequence;
}
return *this;
}
解决方法
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</body>
</html> 参数是对 sequence 对象的引用。但是 std::vector::erase() 没有被限定为 const std::vector<DataType> 方法，因为它修改了 const 的内容，所以它不能在 vector 对象上调用。这就是错误消息试图告诉您的内容 - 正在对 const 对象调用 erase()。