CODEWITHSUNDEEP
c++stringvectoriterator
shewhorn
shewhorn

Reputation: 41

How do I iterate through a string contained in a vector?

For clarity, I am not asking how to iterate through a vector of strings (which is what all of my searches turn up), I want to iterate through a string contained in a vector of strings. I'm running into linker errors when trying to assign the string iterator a value from a string in a vector.

The code below takes a reference to a const vector of strings. The purpose of the function is to reverse the order of the letters and the elements so if you passed in a vector of strings containing { "abc", "def", "ghi" } it would reorder them and return a vector of strings containing { "ihg", "fed", "cba" }. It should be noted that the function is declared as static in the header file. I'm running into a problem when I try to attempt to initialize the string iterator in the for loop. I get a linker error:

"No matching constructor for initialization of 'std::__1::__wrap_iter<char*>'

I thought accessing rbegin() through the -> from the vector iterator would work but... I'm stumped. Why does stringsVectorIterator->rend() cause a linker error when assigned to string::reverse_iterator rit?

vector<string>  StringUtility::reverse(const vector<string> &strings)
{
    // Create a vector of strings with the same size vector as the one being passed in.
    vector<string> returnValue( strings.size() );
    vector<string>::const_reverse_iterator stringsVectorIterator;
    size_t returnVectorCounter;

    for (stringsVectorIterator = strings.rbegin(), returnVectorCounter = 0;
         stringsVectorIterator != strings.rend();
         stringsVectorIterator++, returnVectorCounter++)
    {
        // the problem is in the initialization of the string iterator, it creates
        // a linker error.
        for (string::reverse_iterator rit = stringsVectorIterator->rbegin();
             rit != stringsVectorIterator->rend();
             ++rit)
        {
            returnValue[returnVectorCounter].push_back(*rit);
        }
    }
    return returnValue;
};

Upvotes: 0

Views: 137

Answers (1)

Mike Seymour
Mike Seymour

Reputation: 254431

stringsVectorIterator is a const iterator, so its target string is const. This means you can't get a non-const iterator over the string.

Change the inner loop:

 for (string::const_reverse_iterator rit = ...
              ^^^^^^

and all should be well.

In C++11 or later, you could use auto to avoid these hassles.

Upvotes: 5

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