Instantiating predicates

A predicate in Sway can be as simple as the following:

In this minimal example, the main function does not accept any parameters and simply returns true.

Just like contracts in Sway, once you've created a predicate, you can compile it using forc build. For more information on working with Sway, refer to the Sway documentation.

After compiling, you will obtain the binary of the predicate and its JSON ABI (Application Binary Interface). Using these, you can instantiate a predicate in TypeScript as shown in the code snippet below:

The created Predicate instance, among other things, has three important properties: the predicate bytes (byte code), the chainId, and the predicate address.

This address, generated from the byte code, corresponds to the Pay-to-Script-Hash (P2SH) address used in Bitcoin.

Predicate with multiple arguments

You can pass more than one argument to a predicate. For example, this is a predicate that evaluates to true if the two arguments are not equal:

You can pass the two arguments to this predicate like this:

Predicate with a Struct argument

You can also pass a struct as an argument to a predicate. This is one such predicate that expects a struct as an argument:

You can pass a struct as an argument to this predicate like this: