1. Currently, invoke can be only used from migration scripts. We will add invoke and call commands in a future release.
https://github.com/software-mansion/protostar/issues/883
2. I couldn't replicate this problem. The migration script runner doesn't validate hints. I think the issue may be in the contract. Does this issue occur for the "main" contract generated by protostar init? Maybe the main.json is outdated. How do you run migration scripts?

You can check our integration tests for the invoke cheatcode in the version 0.4.2: https://github.com/software-mansion/protostar/blob/53cb5dc5cda1a74a1ffb862d84e7035e44a5c56b/tests/integration/migrator/migrator_invoke_cheatcode_test.py
(The deploy_contract cheatcode will be deprecated in the next release. Declare cheatcode should be used instead.)

Regarding best practices, migration scripts are intended to be used with Proxy pattern. Protostar's migrations are inspired by Truffle.
https://trufflesuite.com/docs/truffle/getting-started/running-migrations/

FYI: migrations needs polishing. In 0.4.3 for example, you should be able to deploy or declare contract by specifying a contract name (e.g. declare("main")) to avoid using outdated compiled contract by accident.

_This answer was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Newton

Some questions that could be answered separately.

1. The only way to invoke a contract is using migrations (this applies for both devnet and testnet?)
2. When doing a migration file I receive the “Hint is not whitelisted. This may indicate that this library function cannot be used in StarkNet contracts.” error. For example for this code:

```
%lang starknet

@external
func up() {
    %{
        contract_address = deploy_contract(
             "./build/main.json",
             config={"wait_for_acceptance": True}
        ).contract_address

        invoke(
            contract_address,
            "initialize",
            {"new_authority": 123},
            config={
                "auto_estimate_fee": True,
                "wait_for_acceptance": True,
            }
        )
    %}

    return ();
}
```

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

The only way to invoke a contract is using migrations (this applies for both devnet and testnet?)

Hello! This is day 12 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Structs.  Perhaps you can help me?

```
// In this challenge you're going to implement a stack using a linked list.
//
// Add the missing code so that main() runs successfully.

from starkware.cairo.common.registers import get_fp_and_pc

struct Node {
    // A pointer to the next node in the stack.
    next: Node*,

    // The value of the node.
    value: felt,

    // The number of elements in the stack.
    size: felt,
}

// Returns an empty stack.
func empty_stack() -> (stack: Node*) {
    alloc_locals;
    local new_node: Node;
    assert new_node.next = cast(0, Node*);
    assert new_node.value = 0;
    assert new_node.size = 0;

    // The usage of get_fp_and_pc() here is necessary in order
    // to access the address of a local variable (&new_node).
    // You can read more about get_fp_and_pc() [here](https://cairo-lang.org/docs/how_cairo_works/functions.html#retrieving-registers).
    let (local __fp__, _) = get_fp_and_pc();
    return (stack=&new_node);
}

// Adds a node to the top of the stack.
// Returns the updated stack (since Cairo is immutable, you can still use the
// old copy of the stack).
func push(stack: Node*, value: felt) -> (stack: Node*) {
    alloc_locals;
    local new_node: Node;
    // Fix and uncomment below.
    // assert new_node.next = ...
    // assert new_node.value = ...
    // assert new_node.size = ...

    let (__fp__, _) = get_fp_and_pc();
    return (stack=&new_node);
}

// Removes the top element of the stack.
// Returns the updated stack and the element that was removed.
func pop(stack: Node*) -> (stack: Node*, value: felt) {
    return (stack=stack.next, value=stack.value);
}

// Returns the value of the n-th element from the top of the stack.
func stack_at(stack: Node*, n: felt) -> (value: felt) {
    if (n == 0) {
        // Add your code here.
    }

    // Add your code here.
}

func main() -> () {
    alloc_locals;
    // Start with an empty stack.
    let (stack) = empty_stack();
    // Push 1, 10, 100.
    let (stack) = push(stack, 1);
    let (stack) = push(stack, 10);
    let (local stack) = push(stack, 100);

    // Check the size of the stack.
    assert stack.size = 3;

    // Query the stack at indices 0, 1 and 2.
    let (value) = stack_at(stack, 0);
    assert value = 100;
    let (value) = stack_at(stack, 1);
    assert value = 10;
    let (value) = stack_at(stack, 2);
    assert value = 1;

    // Pop the top 2 values (100 and 10) and push 1000.
    let (stack, value) = pop(stack);
    assert value = 100;
    let (stack, value) = pop(stack);
    assert value = 10;
    let (local stack) = push(stack, 1000);

    // Query the stack at indices 0 and 1.
    let (value) = stack_at(stack, 0);
    assert value = 1000;
    let (value) = stack_at(stack, 1);
    assert value = 1;

    return ();
}
```

---

> Answers to this question are a part of the ✨ 17 days of Cairo Lang with Playground & Newton. ✨
> 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

How to create Structs in Cairo Lang for StarkNet?

# Will Kakarot be an L3 on top of the Starknet validity rollup?

Will Kakarot be an L3 on top of the Starknet validity rollup?

Hey there! 

I am using the Oz Nile framework for smart contract development on Starknet. More specifically, I am testing the proxy upgrade feature, but my tests fail with the error message TypeError: int() can't convert non-string with explicit base. This happens when nile.signer tries to sign a transaction. Here's the snippet in the stack trace below. 

```
def sign_transaction(self, sender, calls, nonce, max_fee):
        """Sign a transaction for an Account."""
        (call_array, calldata) = from_call_to_call_array(calls)
        message_hash = get_transaction_hash(
>           int(sender, 16), call_array, calldata, nonce, int(max_fee)
        )
```

Some relevant info:
cairo-lang==0.10.0
cairo-nile==0.8.2
openzeppelin-cairo-contracts==0.4.0b
pytest==7.1.2
python=3.9 

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Cairo/Nile: Testing the proxy upgrade feature, but my tests fail with the error message TypeError: int() can't convert non-string with explicit base.

does cross-chain bridge produce its own block? or it only verify the blocks from A/B chain?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Does cross-chain bridge produce its own block? Or it only verify the blocks from A/B chain?

I made an example using [this library with react](https://github.com/fracek/starknet-react-example), everything is working fine in development, but in production, it looks like starknet.js is throwing a type error. You can [open this page](http://starknet-react-example.vercel.app/) to see the error more in detail.

To reproduce locally:

- Clone my example repo
- Build with `yarn run build`
- Serve production build with `yarn run serve`

Based on this [Github thread](https://github.com/0xs34n/starknet.js/issues/37)

How do I use Create React App in StarknetJS?

Guys, what`s ArgentX?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

What is ArgentX?

does anyone know of newsletters that focus on StarkNet or the zk ecosystem in general?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

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