Remove duplicates in vector of structure c++

Question

I have the following structure. I want to store the structure in a vector. Second i want to remove duplicate values on (context). What am I doing wrong?

---

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

//Structure
struct contextElement
{
  string context;
  float x;
};

int main()
{
  vector<contextElement> v1;
  v1.push_back({"1",1.0});
  v1.push_back({"2",2.0});
  v1.push_back({"1",1.0});
  v1.push_back({"1",1.0});
  //ERROR here
  auto comp = [] ( const contextElement& lhs, const contextElement& rhs ) {return lhs.context == rhs.context;};
  //Remove elements that have the same context
  v1.erase(std::unique(v1.begin(), v1.end(),comp));
  for(size_t i = 0; i < v1.size();i++)
  {
    cout << v1[i].context <<"  ";
  }
  cout << endl;
  return 0;
}

---

Error:

main.cpp|23|error: no matching function for call to 'std::vector::erase(__gnu_cxx::__normal_iterator >, std::vector::iterator, main()::__lambda0&)'|

---

possible Solution

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

//Structure
struct contextElement
{
  string context;
  float x;
};

int main()
{
  vector<contextElement> v1;
  v1.push_back({"1",1.0});
  v1.push_back({"2",2.0});
  v1.push_back({"1",1.0});
  v1.push_back({"1",1.0});
  //sort elements@HaniGoc: unique only removes consecutive duplicates. If you want to move all //duplicates, then either sort it first, or do something more complicated. –  Mike Seymour
  auto comp = [] ( const contextElement& lhs, const contextElement& rhs ) {return lhs.context < rhs.context;};
  sort(v1.begin(), v1.end(),comp);

  auto comp1 = [] ( const contextElement& lhs, const contextElement& rhs ) {return lhs.context == rhs.context;};
  auto last = std::unique(v1.begin(), v1.end(),comp1);
  v1.erase(last, v1.end());

  for(size_t i = 0; i < v1.size();i++)
  {
    cout << v1[i].context <<"  ";
  }
  return 0;
}

Answer 1

vector::erase() does not take a predicate. And your predicate to std::unique should check for equality.