How can I return an array of struct in solidity?

by

As you mentioned, this is not yet supported in Solidity. The powers that be are planning on changing it so you can, but for now, you have to retrieve the number of elements and then retrieve the decomposed struct as a tuple.

function getBidCount(bytes32 name) public constant returns (uint) {
    return highestBidder[name].length;
}

function getBid(bytes32 name, uint index) public constant returns (address, uint, bytes32) {
    Bid storage bid = highestBidder[name][index];

    return (bid.bidOwner, bid.bidAmount, bid.nameEntity);
}

Edit to address question in comment regarding storage vs memory in this case

Local storage variables are pointers to state variables (which are always in storage). From the Solidity docs:

The type of the local variable x is uint[] storage, but since storage is not dynamically allocated, it has to be assigned from a state variable before it can be used. So no space in storage will be allocated for x, but instead it functions only as an alias for a pre-existing variable in storage.

This is referring to an example where the varable used is uint[] x. Same applies to my code with Bid bid. In other words, no new storage is being created.

In terms of cost:

getBid("foo", 0) using Bid memory bid:

enter image description here

getBid("foo", 0) using Bid storage bid:

enter image description here

In this case, storage is cheaper.

More Related Contents:

  1. How to create the most compact mapping n → isprime(n) up to a limit N?
  2. Implement a queue in which push_rear(), pop_front() and get_min() are all constant time operations
  3. Hash table runtime complexity (insert, search and delete)
  4. Data structures for loaded dice?
  5. Find kth smallest element in a binary search tree in Optimum way
  6. How to implement a queue using two stacks?
  7. How do you validate a binary search tree?
  8. design a stack such that getMinimum( ) should be O(1)
  9. Computing set intersection in linear time?
  10. Best algorithm to test if a linked list has a cycle
  11. How to delete in a heap data structure?
  12. Array remove duplicate elements
  13. What is the difference between tree depth and height?
  14. How Do I Choose Between a Hash Table and a Trie (Prefix Tree)?
  15. What is the fastest way to find the closest point to a given point?
  16. insert, delete, max in O(1)
  17. O(klogk) time algorithm to find kth smallest element from a binary heap
  18. In Order Successor in Binary Search Tree
  19. Skip List vs. Binary Search Tree
  20. Algorithm for autocomplete?
  21. Hashing a Tree Structure
  22. graph – Dijkstra for The Single-Source Longest Path
  23. What is the advantage to using Bloom filters?
  24. Search a sorted 2D matrix [duplicate]
  25. Why increase pointer by two while finding loop in linked list, why not 3,4,5?
  26. Why use binary search if there’s ternary search?
  27. Why are hash table expansions usually done by doubling the size?
  28. What are probabilistic data structures?
  29. How to find the number of different shortest paths between two vertices, in directed graph and with linear-time?
  30. Given a set of intervals, find the interval which has the maximum number of intersections

Leave a Comment