Is it possible to get networkid inside the contract

Question

I started my private network with id = 15452:

geth --networkid 15452

Is it possible to get the number inside solidity smart contract?

Answer 1

I don't think that's possible because by design there is clear separation between the EVM (turing machine) and the Ethereum network.

In the same manner as a virtual machine on your PC, it is sandboxed and isolated from the network, whilst still being a part of it. This isolation is what makes it impervious to hack attacks and corruption, essentially fortifying it.

However, you could simply do this in the contrat

pragma solidity ^0.5.2;

contract MyContract {
    uint networkid;

    constructor(uint _networkid) public {
        networkid = _networkid;
    }
}

Answer 2

Chainlink is doing something clever. They deployed a contract on each network with the same account and nonce. This means the contract will have the same address in each network.

address constant private LINK_TOKEN_POINTER = 0xC89bD4E1632D3A43CB03AAAd5262cbe4038Bc571;

Then they use this address to receive the proper address for the LINK token. You could basically do the same and add functions to the LINK_TOKEN_POINTER contract as you need them.

Full contract at https://github.com/smartcontractkit/chainlink/blob/develop/evm-contracts/src/v0.6/ChainlinkClient.sol