Array of struct inside and a array

Question

It´s posible to save structs inside array and all this array´s inside the same array. I mean:

[ [{"struct"}, {"struct"}, {"struct"}], [ {"struct"}, {"struct"}], [{"struct"}, {"struct"}, {"struct"}, {"struct"}] ]

I can´t find something related to this in the web.

And is efficient to implement this storage system. If the array is so big can increment the transaction cost. Is profitable?

Answer 1

Yes, you can have an array of array of struct.

pragma solidity >= 0.4.25 < 0.6;

contract Bank {
    struct Customer {
        uint age;
    }
    Customer[][] customers;
    function foo() public {
        if (customers.length > 0) {
            Customer[] storage northBranch = customers[0];
            if (northBranch.length > 1) {
                Customer storage customer = northBranch[1];
                customer.age = 23;
            }
        } else {
            Customer memory bob;
            bob.age = 34;
            customers.length += 1;
            customers[0].push(bob);
        }
    }
}

For the other answers I'd say it depends on the particular use.