mutate

A transaction execution function that allows you to submit Cadence transactions to the Flow blockchain to mutate on-chain state. This function handles the complete transaction lifecycle including building, signing, and sending transactions to Flow. It provides a high-level interface that abstracts the complexity of transaction construction while offering flexibility for advanced use cases.

The mutate function automatically handles authorization using the current authenticated user by default, but allows for custom authorization functions to be specified for different transaction roles (proposer, payer, authorizer). It supports both simple single-party transactions and complex multi-party transactions with different signatories.

This function integrates with FCL's address replacement system, allowing you to use placeholder addresses in your Cadence code that are replaced with actual addresses at execution time. It also supports Interaction Templates for standardized transaction execution patterns.

The mutate function accepts a configuration object with the following structure:

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{

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cadence?: string, // The Cadence transaction code to execute (required if template not provided)

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args?: Function, // Function that returns an array of arguments for the transaction

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template?: any, // Interaction Template object or URL for standardized transactions

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limit?: number, // Compute (gas) limit for the transaction execution

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authz?: AccountAuthorization, // Authorization function for all signatory roles (proposer, payer, authorizer)

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proposer?: AccountAuthorization, // Specific authorization function for the proposer role

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payer?: AccountAuthorization, // Specific authorization function for the payer role

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authorizations?: AccountAuthorization[] // Array of authorization functions for authorizer roles

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}

Import

You can import the entire package and access the function:

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import * as fcl from "@onflow/fcl"

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fcl.mutate(opts)

Or import directly the specific function:

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import { mutate } from "@onflow/fcl"

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mutate(opts)

Usage

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// Basic transaction submission

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import * as fcl from "@onflow/fcl"

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// Configure FCL first

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fcl.config({

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"accessNode.api": "https://rest-testnet.onflow.org",

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"discovery.wallet": "https://fcl-discovery.onflow.org/testnet/authn",

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"flow.network": "testnet"

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})

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// Authenticate user

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await fcl.authenticate()

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// Submit a basic transaction

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const txId = await fcl.mutate({

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cadence: `

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transaction(message: String) {

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prepare(account: AuthAccount) {

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log("Transaction executed by: ".concat(account.address.toString()))

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log("Message: ".concat(message))

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}

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}

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`,

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args: (arg, t) => [

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arg("Hello Flow!", t.String)

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],

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limit: 50

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})

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console.log("Transaction submitted:", txId)

Parameters

opts

• Type: any
• Description: Transaction configuration options

Returns

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(opts?: MutateOptions) => Promise<string>

Promise that resolves to the transaction ID (txId) when the transaction is submitted

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