So far during this tutorial we have not concerned ourselves with specifying meaningful outcomes on any of our
States. This has meant that although we have learnt to deposit assets, execute state transitions off chain, and to finalize an outcome via challenge or conclude, no participant could get their funds back out of the state channel and into their ethereum account.
The time has come to tackle this issue!
Nitro protocol is an extension of ForceMove protocol that we have dealt with so far. ForceMove specifies only that a state should have a default
outcome but does not specify the format of that
outcome, and simply treats it as an unstructured
bytes field. In this section we look at the outcome formats needed for Nitro.
Nitro supports multiple different assets (e.g. ETH and one or more ERC20s) being held in the same channel.
Outcomes that allocate
An Allocation outcome specifies
- at least one asset (such as ETH or an ERC20 token).
- for each asset, an array of (destination, amount) pairs known as an
Allocation, and indicating a payout of amount tokens to destination.
asset is used to store to the address of the ERC20 token contract. It can also be set to the zero address, and this implies the native token ETH.
The destination here might be an external destination (which means the assets will get paid out to an ethereum address) or a channelId. In the code snippet below, we import
convertAddressToBytes32 to convert an ethereum address to an external destination.
In nitro protocol, channels can allocate funds to other channels!
To construct an outcome, you can import the
Outcome type to ensure you're getting the basics right. Then go ahead and attach that outcome in place of the
 we used as a placeholder previously on our
Outcomes that guarantee
Guarantee Asset Outcomes are similar to Allocation Asset Outcomes, only they do not have any amounts. Their purpose is to simply express an ordering of destinations for a given asset (say, a given token).
A channel that has a guarantee outcome is said to be a guarantor channel.
Now while we can transfer assets out of a channel, the terminology is instead to claim on a guarantor channel. Assets will be paid to beneficiaries of the target channel, but in an order of precedence defined by the guarantor. More on this later.
For simplicity, the on-chain code assumes that neither kind of allocation has any repeated entries.
Constructing the right kind of object in typescript is straightforward:
Encoding of all outcomes (including guarantee outcomes) is handled seamlessly by the
Don't worry if it is not yet clear why we need guarantor channels or outcomes that guarantee. They are a useful tool for virtually funding channels, but can be safely ignored if you are just trying to understand directly funded channels.