Icon LinkString

In Sway, strings are statically-sized, which means you must define the size of the string beforehand. Statically-sized strings are represented using the str[x] syntax, where x indicates the string's size. This guide explains how to create and interact with statically-sized strings while using the SDK.

Icon LinkCreating Statically-Sized Strings

// Sway str[2]
const stringSize2 = 'st';
 
// Sway str[8]
const stringSize8 = 'fuel-sdk';

Icon LinkInteracting with Statically-Sized Strings in Contract Methods

When a contract method accepts and returns a str[8], the corresponding SDK wrapper method will also take and return a string of the same length. You can pass a string to the contract method like this:

const { value } = await contract.functions
	.echo_str_8('fuel-sdk')
	.txParams({ gasLimit: 10_000 })
	.simulate();
 
expect(value).toEqual('fuel-sdk');

When working with statically-sized strings, ensure that the input and output strings have the correct length to avoid erroneous behavior.

If you pass a string that is either too long or too short for a contract method, the call will fail like this:

const longString = 'fuel-sdk-WILL-THROW-ERROR';
 
await expect(async () =>
	contract.functions.echo_str_8(longString).txParams({ gasPrice }).call()
).rejects.toThrowError('Value length mismatch during encode');
 
const shortString = 'THROWS';
 
await expect(async () =>
	contract.functions.echo_str_8(shortString).txParams({ gasPrice }).call()
).rejects.toThrowError('Value length mismatch during encode');