Post Conditions

Clarigen can make it easier for you to write post conditions in your app.

NFT Post Conditions

To create a NFT post condition, use makeNonFungiblePostCondition.

The arguments are:

contract: a Clarigen-created contract (see factories)
address: The address that this post condition is for
condition: An NFTConditionCode
value: the asset ID for this post condition.

For this example, assume there is an NFT contract defined like this:

(define-non-fungible-token punks uint)

To create a post condition:

import { makeNonFungiblePostCondition } from '@clarigen/core';
import { NonFungibleConditionCode } from 'micro-stacks/transactions';
import { nftContract } from './contracts';
 
const sender = 'SP12...';
 
const postCondition = makeNonFungiblePostCondition(
  nftContract,
  sender,
  NonFungibleConditionCode.DoesNotOwn,
  1n // the ID of the NFT
);

Note that this is strongly typed, so using a value other than a bigint as an ID would show a type error.

If the NFT has a different type of key, like for BNS:

(define-non-fungible-token names { name: (buff 48), namespace: (buff 20) })

Then you'd need to use an appropriate tuple type:

const postCondition = makeNonFungiblePostCondition(
  nftContract,
  sender,
  NonFungibleConditionCode.DoesNotOwn,
  {
    name: asciiToBytes('example'),
    namespace: asciiToBytes('btc'),
  }
);

Fungible token post conditions

Creating post conditions for a fungible token follows a similar process, except that you use an amount instead of a specific NFT.

When calling makeFungiblePostCondition, the amount argument can be:

A bigint (123n)
A string-encoded integer ("123")
A number type integer (123)

import { makeFungiblePostCondition } from '@clarigen/core';
import { FungibleConditionCode } from 'micro-stacks/transactions';
import { ftContract } from './contracts';
 
const sender = 'SP12...';
 
const postCondition = makeFungiblePostCondition(
  ftContract,
  sender,
  FungibleConditionCode.Equals,
  1000n // the amount being sent
);