CODEWITHSUNDEEP
c++stl
SIGSTP
SIGSTP

Reputation: 1155

Finding an iterator corresponding to an object stored in a vector

I have a vector v containing objects of type structure say A. Now I need to find the iterator for a particular object stored in this vector. e.g:

  struct a
    {
    };
    vector<a> v;
    struct temp;  //initialized

Now if I will use 

find(v.begin(),v.end(), temp);

then compiler generates error saying no match for operator '=='.

Any workaround for getting an iterator corresponding to an object in a vector?

Upvotes: 0

Views: 119

Answers (1)

juanchopanza
juanchopanza

Reputation: 227390

You have to provide either a bool operator==(const a& lhs, const a& rhs) equality operator for your class, or pass a comparison functor to std::find_if:

struct FindHelper
{
  FindHelper(const a& elem) : elem_(elem) {}
  bool operator()(const a& obj) const
  {
  // implement equality logic here using elem_ and obj
  }
  const a& elem_;
};

vector<a> v;
a temp;
auto it = std::find_if(v.begin(), v.end(), FindHelper(temp));

Alternatively, in c++11 you can use a lambda function instead of the functor.

auto it = std::find_if(v.begin(), v.end(),  
                       [&temp](const a& elem) { /* implement logic here */ });

Upvotes: 2

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