I have following code piece:

  struct PaymentReceipt{
    uint   start_block;
    uint   end_block;
  PaymentReceipt[] paymentReceiptList;

  function verfiyPayment(uint block_start, uint block_end) returns (bool success) {
    paymentReceiptList.push(PaymentReceipt({start_block: block_start, end_block: block_end }));
    return true;

As I know, each new Struct will be pushed on top of the stack, so latest element (paymentReceiptList.length) will always point to the latest pushed Struct.


Dynamically-sized storage arrays have a member function push, such that var l = arr.push(el); is equivalent to arr[arr.length++] = el; var l = arr.length;.

For example, Java has following approach that: we can insert the specific element at the specified position in the list.

[Q] Is it possible to push an object into an Array with a given index and shift indexes, like the example on Java?

2 Answers 2


There is no built-in method for inserting a value at a specific position in an array. You'll just have to write a loop to do it.

If you're going to be inserting a lot of elements in the middle of the array, it may make more sense to use a linked list instead of an array, so that you aren't doing as many storage writes, which can be expensive.

  • I am thinking to implement LinkedList as the implementation in C as via pointer. In order to do that I need to allocate memory space for node and its address. I was not able to obtain its address. struct node{ uint data; uint next; } node head = node(0,0); is it possible to get head's address in the memory?
    – alper
    Commented Jan 29, 2017 at 13:09
  • 1
    I'm not exactly sure what you're asking. For a linked list, you need to keep a pointer to the head separate from the rest of the data structure. Commented Jan 29, 2017 at 18:12

A bit outdated answer, but still :) If you can assume you gonna insert no more than N elements at the beginning, you could just reserve them in advance and allocate array size of usual_size + N elements. Also you keep variable offset, so any accessing will be like myArray[offset + i]

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