How to download array of strings

Question

EOS requires token holders to generate public keys and register them, by using their "register" function in their smart contract. Here's the function (copied from Etherscan):

mapping (address => string) public keys;
...
event LogRegister (address user, string key);    
...
// Value should be a public key.  Read full key import policy.
// Manually registering requires a base58
// encoded using the STEEM, BTS, or EOS public key format.
function register(string key) {
    assert(today() <=  numberOfDays + 1);
    assert(bytes(key).length <= 64);

    keys[msg.sender] = key;

    LogRegister(msg.sender, key);
}

They store the public keys in:

keys[msg.sender] = key;

I'm thinking of doing something similar, but I do not see how EOS extracts and downloads the "keys" array. EOS does not have a function to iterate through this array and to return the values. How does one download the "keys" array?

Is it possible to get all of the values from "keys" from Etherscan (because of LogRegister event)? If so, how?

Answer 1

In the declaration of the variable, the keyword public is used:

mapping (address => string) public keys;

Not:

mapping (address => string) keys;

When that public` keyword is set like that, Solidity makes a getter function with the same name as the variable automatically when compiled.

Hence, when looking at the EOS contract in Etherscan, under the "Read Smart Contract" tab, there's a "keys" option. However, it does not present the whole map to you; you must know the address you wish to look up in order to get just that value back. For EOS's application's purposes, it must not have a need for an exhaustive list of everyone's keys, it typically only would care about the keys of the account interacting with it, so the default getter works just fine for that purpose.

To get a list of all records in that mapping, yes, you could use the JSON-RPC methods or web3js methods to query all the LogRegister events, and build up the complete list.