View Source Typed Arguments

Typed arguments help Ethers with determining the exact function to use when there are multiple overloads of the same function with same arity.

Problem

In solidity, contract functions (and events) can be overloaded. This means a function with the same name can be defined with different argument types and even different arities.

Example

contract Overloaded {
    function transfer(uint256 amount) public pure returns (string memory) {
        ...
    }

    function transfer(int256 amount) public pure returns (string memory) {
        ...
    }
}

In the above contract, the function transfer is once implemented with uint256 and another time with int256.

Since Elixir is dynamically typed, we need a way to specify which function we need to call in this scenario.

Solution

Ethers provides a simple helper function called Ethers.Types.typed/2. This function helps you with specifying the type for your parameter. It will help Ethers to know which function to select when you want to call it.

Let's try it with the example contract above. If we assume we want to call the transfer function with uint256 type, here is the code we need.

defmodule Overloaded do
  use Ethers.Contract, abi: ...
end

Overloaded.transfer(Ethers.Types.typed({:uint, 256}, 100))
|> Ethers.send!(...)

This way we have explicitly told Ethers to use the uint256 type for the first argument.

Supported Types

Ethers supports all generic data types from EVM. Here is a list of them.