Ethereum: TypeError: X is not a function (Uncaught (in promise) error)

Ethereum Error: TypeError: X is not a function

As a developer working with Ethereum smart contracts, you may be no stranger to the complex world of programming languages ​​and libraries. However, when using certain methods in your Ethereum contract, you may encounter an error that at first glance seems trivial. In this article, we will look at the specifics of the cause of this issue and provide a solution.

Problem: TypeError: X is not a function

When you try to call a method in your Ethereum contract using contract.methods.methodName(), it will throw an error stating that X is not a function. While this may seem like a generic error message, it is actually more specific.

Problem: Unbound Constructor

In many programming languages, including JavaScript and some other libraries, when you call a method on an object, without specifying the object itself (i.e. X), it will look for a constructor function defined elsewhere. However, in this case we are working with a contract, not a class.

Fix: Constructor Binding

To fix this problem, you need to bind the constructor of your contract method to an instance of the contract itself. This is done using the bind() method provided by the call function.

`JavaScript

In this example, we bind themyMethodconstructor tothis(i.e., our contract instance), which allows us to call it without specifyingX.

Best Practices
To avoid similar problems in the future:
Make sure your methods are defined as constructors (constructor X()) instead of regular functions.
Use thebind()method when calling a method on a contract instance.
By applying these fixes and best practices, you should be able to resolve the TypeError: X is not a function error associated with your Ethereum smart contract.

Code Example
Here is an example of a code snippet that shows how to resolve this issue:
JavaScript
import * as ether fromethers'';
const MyContract = artifacts.require('MyContract');
contract('MyContract', async (account) => {
await const instance = MyContract.new();
const myMethod = instance.methods.myMethod;
// Call myMethod without specifying X
await console.log(myMethod()); // Output: TypeError: X is not a function
// By using bind() to specify this, we solve the problem:
await const result = myMethod.bind(this).call();
console.log(result);
});

Replace `MyContract` with the actual name of your contract and change the code accordingly.