Properly format Struct array that's returned?

[dvlden]

Searching the docs, this utility doesn't seem to exist.
I am returning the array of structs from my contract. Used hardhat to compile contract, types and for a deployment.

I am unsure if this is how it's returned in other web3 libs too or it's specific to ethers?

Here's the part of the actual response that I receive:

[{
    0: {
        "_hex": "0x00",
        "_isBigNumber": true
    },
    1: 'new item',
    2: 0,
    id: {
        "_hex": "0x00",
        "_isBigNumber": true
    },
    length: 3,
    status: 0,
    text: 'new item'
}]

The actual struct type in solidity is:

enum ItemStatus {
    Pending,
    Completed,
    Deleted
}
  
struct Item {
    uint256 id;
    string text;
    ItemStatus status;
  }

Expected response?

[{
    id: {
        "_hex": "0x00",
        "_isBigNumber": true
    },
    status: 0,
    text: 'new item'
}]

Am I missing something? Is there an util from ethers that can format this to expectation? Optionally the ID should become a number as well, not object that needs util format.

[ricmoo]

The result type is a normal array, but also includes names properties to access values, for convenience.

So, you can use item.text or item[1], for example to get the text entry.

The id is a uint256 so it must be a BigNumber (which you can use any of the BigNumber serializing methods on). In JavaScript, numbers must be 53 or fewer bits otherwise they suffer rounding and corruption. The type defines what is returned, so if you had a struct of uint48 for the id you would get a number back.

Does that make sense?

[dvlden]

Yes, I understand the logic. However it'd be nice if it was:

• Only array by default
• Only object if specified

Cause with current implementation, I need to iterate through, picking only props that have strings as keys and avoid length prop.
Is there an approach to do this already?

[marcustut]

For the moment, I'm using this as a workaround.

// convertToStruct takes an array type eg. Inventory.ItemStructOutput and converts it to an object type.
export const convertToStruct = <A extends Array<unknown>>(arr: A): ExtractPropsFromArray<A> => {
  const keys = Object.keys(arr).filter((key) => isNaN(Number(key)));
  const result = {};
  // @ts-ignore
  arr.forEach((item, index) => (result[keys[index]] = item));
  return result as A;
};

// This is to remove unnecessary properties from the output type. Use it eg. `ExtractPropsFromArray<Inventory.ItemStructOutput>`
export type ExtractPropsFromArray<T> = Omit<T, keyof Array<unknown> | `${number}`>;

[lucabrini]

I've written this workaround. It returns an object.

export function fromStructToObject<T extends object>(struct : [] & T) : T{
    
    struct = {...struct};
    const keysNumber = Object.keys(struct).length;
    for(var i = 0; i < keysNumber/2; i++){
        delete struct[i];
    }

    return struct;
}

Then you could do something like this to get the array of the struct

Object.values(fromStructToObject(struct))