c++ - 找不到 operator= 的匹配项(在 vector 中查找值)

Question

我显然在这里遗漏了什么，但是什么？

定义(...表示有效代码，不是实际的三点):

class CrmxFile {
private:
    const std::vector<std::string> validValues;
    int value;

public:
    void setValue(std::string _value);

...
}

std::vector<std::string> CrmxFile = {...};

在我的代码中:

void Crmx::SetValue(std::string _value) {
    std::vector<std::string>::iterator idx;
    if((idx = std::find(validValues.begin(), validValues.end(), _value)) == validValues.end()) {
        value = 0;
    }
    else {
        value = idx - validValues.begin();
    }
}

我用 gcc -c -std=c++0x 编译它，我得到这个错误:

CrmxFile.cpp: In member function ‘void CrmxFile::SetValue(std::string)’:
CrmxFile.cpp:24:64: error: no match for ‘operator=’ in ‘idx = std::find [with _IIter = __gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >, _Tp = std::basic_string<char>](Id3V1::validValues.std::vector<_Tp, _Alloc>::begin [with _Tp = std::basic_string<char>, _Alloc = std::allocator<std::basic_string<char> >, std::vector<_Tp, _Alloc>::const_iterator = __gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >, typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::const_pointer = const std::basic_string<char>*](), Id3V1::validValues.std::vector<_Tp, _Alloc>::end [with _Tp = std::basic_string<char>, _Alloc = std::allocator<std::basic_string<char> >, std::vector<_Tp, _Alloc>::const_iterator = __gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >, typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::const_pointer = const std::basic_string<char>*](), (*(const std::basic_string<char>*)(& _value)))’
CrmxFile.cpp:24:64: note: candidates are:
/usr/include/c++/4.6/bits/stl_iterator.h:702:11: note: __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >& __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >::operator=(const __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >&)
/usr/include/c++/4.6/bits/stl_iterator.h:702:11: note:   no known conversion for argument 1 from ‘__gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >’ to ‘const __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >&’
/usr/include/c++/4.6/bits/stl_iterator.h:702:11: note: __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >& __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >::operator=(__gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >&&)
/usr/include/c++/4.6/bits/stl_iterator.h:702:11: note:   no known conversion for argument 1 from ‘__gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >’ to ‘__gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >&&’

我错过了什么？或者，是否有更好的方法来查找 vector 中给定值的索引？

Answer 1

idx必须是 const_iterator自 validValues是 const vector<...> .

std::vector<std::string>::const_iterator idx;