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ethereumblockchainsoliditysmartcontracts

Can someone explain how below code generates Id for zombies in Solidity?

struct Zombie {
   string name;
   uint dna;
   uint32 level;
   uint32 readyTime;
   uint16 winCount;
   uint16 lossCount;
 }

Zombie[] public zombies;
function _createZombie(string memory _name, uint _dna) internal {
    uint id = zombies.push(Zombie(_name, _dna, 1, uint32(now + cooldownTime), 0, 0)) - 1;
}

Please explain how the above line code uint id generates an id for zombies in the _createZombie function.

Solution

  • When zombies.push() happens, it returns the new length of array zombies so, it gets saved in the id as zombies.length - 1 which gives you current index of the Zombie data stored.

    Note: I guess this code snippet will not run on latest versions of solidity compiler, as there would be some warnings.