Can we typecast string to use it as a id in table?

Question

I need to use a string as a id of table in my smart contract. Initially i found some answers that string can't be use as primary key. But i use string as a key in table as given below:

//@abi table tttab i64
struct tttab
{
    string tableid;
    vector<uint64_t> preowners;
    uint64_t primary_key() const { return eosio::string_to_name(tableid.c_str()); }

    EOSLIB_SERIALIZE(tttab, (tableid)(preowners))
};

typedef multi_index<N(tttab), tttab> __mytable;

this works fine for me. My question is : Is this a right approach to use string as a id?

Answer 1

eosio::name is uint64_t internally and encodes string with BASE32. If you are sure that your tableid will contain chars in range of [.1-5a-z] and its length won't exceed 12 (or 13th-char only can have [.1-5a-j]), you can use it as primary key. By the way, the size of string is determined by its length, so if your tableid are expected to be longer than 8 in general case, to set the type of tableid as eosio::name seems to be a better solution.