mapping to a mapping? or mapping to a struct

Question

Is it possible to do something similar to the below? Currently when compiling it will throw an error saying that "Name has to refer to a struct, enum or contract". I also have a "working?" solution further below but I am unsure which would be the proper way.

mapping(address => uint256) shelf;
mapping (address => shelf) bookcase;

The idea being that an address would point to a bookcase which goes to a shelf which goes to an int (number of books).

The below works fine so far for setting the value for the shelf. The problem in this version is that I can not make bookcase public and can't figure out how to create a getter.

struct shelf
{
  mapping(address => uint256) shelves;      
}
mapping (address => shelves) bookcase;
bookcase[msg.sender] = shelf();
//shelf_address is argument from the function this code is in
bookcase[msg.sender].shelves[shelf_address] = 1;

Thanks for the pointers.

Answer 1

This is how to use nested mappings and structs within a mapping.

Accesible through bookcase[--address--][--index--].books / bookcase[--address--][--index--].shelfId In real life you would make the second mapping an array though.

pragma solidity ^0.4.10;

contract Mappings {
    mapping(address => mapping(uint256 => Shelf)) bookcase;
    struct Shelf {
      bytes32[] books;
      uint shelfId;
    }
}