Icon LinkDefining Error Handling

Enumerations, or enums, are a type that can be one of several variations. In our contract, we can use an enum to create custom errors to handle errors in a function.

enum InvalidError {
	IncorrectAssetId: ContractId,
	NotEnoughTokens: u64,
	OnlyOwner: Identity,
}

In our contract, we can expect there to be some different situations where we want to throw an error and prevent the transaction from executing:

1. Someone could try to pay for an item with the wrong currency.
2. Someone could try to buy an item without having enough coins.
3. Someone could try to withdraw funds from the contract who isn't the owner.

We can define the return types for each error. For the IncorrectAssetId error we can return the asset id sent, which is a ContractId type. For the NotEnoughTokens variation, we can return the number of coins by defining the return type as a u64. For the OnlyOwner Error, we can use the Identity of the message sender.