Initializing an array of contracts

Question

I am just starting out with Solidity and I came across this code block meant to deploy a new contract and add the address to an array.

Can someone please explain why the array is initialized this way?

It is different from how I will normally do it in JavaScript

import "./simpleStorage.sol";

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;



contract StorageFactory {

    SimpleStorage[] public simpleStorageArray;

    function createSimpleStorageContract() public {
       SimpleStorage simpleStorage = new SimpleStorage(); 
       simpleStorageArray.push(simpleStorage);
    }
}

Answer 1

In Solidity you can initialize an array like SimpleStorageArray[] variable without specify its length. Only for storage arrays, there is a method called push() that allows to add in queue the element inside array.

In your case, when a user interact for the first time createSimpleStorageContract() in SimpleStorage[] array will add an instance of SimpleStorageArray smart contract inside first index about array. When a user call for the second time this function, the SimpleStorage instance will be insert into second index about array, and so on...

More details about arrays here.