Search multi_index by nonprimary key

Question

#include <eosiolib/eosio.hpp>

using namespace eosio;

class [[eosio::contract("addressbook")]] addressbook : public eosio::contract {

public:
  using contract::contract;

  addressbook(name receiver, name code, datastream<const char*> ds): contract(receiver, code, ds) {}

  [[eosio::action]]
  void upsert(name user, uint64_t id, std::string name, std::string x, std::string y) {
    address_index addresses(_code, _code.value);
    auto iterator = addresses.find(id);
    if( iterator == addresses.end() )
    {
      addresses.emplace(user, [&]( auto& row ) {
       row.id = id;
       row.name = name;
       row.x = x;
       row.y = y;
      });
    } 
  }


private:
  struct [[eosio::table]] names {
    uint64_t id;
    std::string name;
    std::string x;
    std::string y;
    uint64_t primary_key() const { return id; }
  };
  typedef eosio::multi_index<"names"_n, names> address_index;

};

EOSIO_DISPATCH( addressbook, (upsert))

How do I search by name instead of id so I know when to create a new row? How can I make id autoincrement instead of a parameter?

EDIT:

  bool found = false;
  for(auto itr = addresses.begin(); itr != addresses.end() && found!=true;) {
    if(itr->did == did) {
      found = true;
    }      
  }

  if(found == false) {
    addresses.emplace(user, [&]( auto& row ) {
    row.id = addresses.available_primary_key();
    row.did = did;
    row.x = x;
    row.y = y;
    });
  }

Answer 1

So you have to do two things:

1. Set up name as a secondary index
2. Get that index, which can then be used with the find command.

Unfortunately, the string type can not be used for secondary indices, only number types can be used.

Look at the examples given here: https://eosio.github.io/eosio.cdt/1.5.0/group__multiindex.html

Specifically, check out the get_index function.