How to find the length of the mapping or iterate over it?

Question

In sol 0.8.10 I used this approach given by this

contract Campaign {
struct Request {
    string description;
    uint value;
    address recipient;
    bool complete;
    uint approvalCount;
    mapping(address => bool) approvals;
}

uint numRequests;
mapping (uint => Request) requests;

function createRequest(string memory description, uint value, address recipient) 
public restricted {            
    Request storage r = requests[numRequests++];
    r.description = description;
    r.value = value;
    r.recipient = recipient;
    r.complete = false;
    r.approvalCount = 0;
 }
}

function getSummary() public view returns (uint, uint, uint, unit, address) {
return (
  minimumContribution,
  address(this).balance,
  requests.length, // TypeError: Member "length" not found or not visible after argument-dependent lookup in mapping
  approversCount,
  manager
 );
}

How to find the length of this requests mapping?

Answer 1

You cannot iterate over the keys or get a mapping's length, but you do track the number of elements in your mapping in numRequests

See this to complete your approach: How to loop through mapping in solidity?