Question

In defining my Element class I get the following error:

no matching function for call to ‘Dict::Dict()’ word1.cpp:23:
    note: candidates are: Dict::Dict(std::string) word1.cpp:10:
    note: Dict::Dict(const Dict&)

I’m not calling anything, I’m merely letting Element inherit from Dict. What’s the problem here?

The other error is in my Word class constructor I get the following:

In constructor ‘Word::Word(std::string)’: word1.cpp:71:
    note: synthesized method ‘Element::Element()’ first required here

I’m really frustrated at this point as everything seems okay to me.

#include <iostream>
#include <vector>
#include <sstream>
#include <string.h>
#include <fstream>

using namespace std;

class Dict {
   public:
    string line;
    int wordcount;
    string word;
    vector <string> words;

    Dict(string f) {
        ifstream in(f.c_str());
        if (in) {
            while (in >> word) {
                words.push_back(word);
            }
        }
        else cout << "ERROR couldn't open file" << endl;
        in.close();
    }
};

class Element: public Dict { //Error #1 here 
    //Don't need a constructor
    public:
      virtual void complete(const Dict &d) = 0;
      //virtual void check(const Dict &d) = 0;
      //virtual void show() const = 0;
};

class Word: public Element{
    public:
      string temp;
      Word(string s){ // Error #2 here
          temp = s;
      }
      void complete(const Dict &d){cout << d.words[0];}
};

int main()
{
    Dict mark("test.txt"); //Store words of test.txt into vector
    string str = "blah"; //Going to search str against test.txt
    Word w("blah"); //Default constructor of Word would set temp = "blah"
    return 0;
}

Answer 1

You need to provide the constructor taking no arguments for your class Dict, if you are defining any constructor for it yourself.

From where does the no parameter constructor for Dict get invoked?

Word w("blah");

Creates an Word object by calling Word(string s). However, Since Word is derived from Element which in turn is derived from Dict, their default constructors, which take no parameters will be called as well. And you do not have a no parameter constructor defined for Dict So the error.

Solution:
Either to provide a constructor for class Dict which takes no parameters yourself.

Dict()
{
} 

Or
define a constructor in Element which calls one of the parameterized constructors of Dict in the Member Initializer List.

Element():Dict("Dummystring")
{
}