CODEWITHSUNDEEP
c++stringclassconstructor
JoyStickFanatic
JoyStickFanatic

Reputation: 22

what causes c++ std::string variable gives conflicting defenition when passing to class

I have a class that has one constructor that takes a string; when a literal was passed in to create a new instant it worked fine. Now when I create a string variable to have read in it throws an error saying there are conflicting definitions. The variable is able to be passed to a non-class function successfully. Here is the code:

/*********************
*
*
*draw a box around 
*words
*each word gets its 
*own line
*********************/
    #include <iostream>
    #include <fstream>
    #include <string>
    #include <sstream>
    #include <vector>
    using namespace std;


class Box 
{
short width;// allows for an empty box to appear as two lines
short height;// makes an empty box a 2x2 box

string text;
//will only be constructed with a word
public:
Box(string& words): text(words)
{
    height = calc_height()+2;
    cout<<height -2<<endl<<text<<endl;
    width = calc_Max_length();
    cout<<width<<endl<<text;

}
private:
short calc_height()
{
    long total = text.length();
    string space = " ";
    short num_words =1; // calculated by the number of spaces, i know poor option but still hey itll mostly work assuming one word at min
    bool afterword = false;
    for(int i =0; i<text.length(); i++)
    {
        if(text[i] == ' ')
        {

            if(afterword)
            {
                num_words+=1;
                afterword=false;
            }
        }
        else
            {afterword=true;}
    //    cout<<i<<'\t'<<num_words<<endl;

    }
//    cout<<num_words;
    return num_words;

}
short calc_Max_length()
{

    short dist_between =0;
    short max = 0;
    short last = 0;
    bool afterword = false;
        for(int i =0; i<text.length(); i++)
    {
        if(text[i] == ' ')
        {
        //    dist_between = i-last;
            max = dist_between>max?dist_between:max;
            last = i;
            dist_between = 0;

        }
        else
            {
                dist_between++; 
            }
    //    cout<<i<<'\t'<<num_words<<endl;

    }
        max = dist_between>max?dist_between:max;

    return max;
}




};


void takes_string(string& s)
    {
    cout<<s;
    return;
    }


int main(void)
    {   
        string input = "crappy shit that sucks";
        takes_string(input);
    //    cin>>input;
        Box(input);

        return 0;
    }

Upvotes: 1

Views: 1721

Answers (1)

Tony Delroy
Tony Delroy

Reputation: 106068

Box(input);

...is equivalent to...

Box input;

That is, it's trying to create a variable of type Box with identifier input, but there's already a std::string called input, hence the redefinition error.

What you obviously want - a temporary Box constructed from the input string - should be written - in C++11 - like this...

Box{input};

FWIW, a good compiler should make this pretty clear in the error message, e.g. from GCC on coliru.stackedcrooked.com:

main.cpp: In function 'int main()':
main.cpp:99:18: error: conflicting declaration 'Box input'
         Box(input);
                  ^
main.cpp:96:16: note: previous declaration as 'std::string input'
         string input = "crappy shit that sucks";
                ^

Upvotes: 3

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