validator

A builder function that adds a validator to a transaction.

Validators are functions that run during transaction building to check for invalid configurations or parameters. They help catch errors early before submitting transactions to the network, preventing failed transactions and wasted compute costs.

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.validator(cb);

Or import directly the specific function:

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import { validator } from '@onflow/fcl';

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validator(cb);

Usage

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import * as fcl from '@onflow/fcl';

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// Custom validator to ensure account has sufficient balance

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const validateBalance = (ix) => {

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if (ix.message.computeLimit > 1000) {

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throw new Error('Compute limit too high for this account');

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}

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return ix;

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};

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await fcl.send([

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fcl.transaction`

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transaction {

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prepare(account: AuthAccount) {

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// Transaction logic

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}

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}

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`,

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fcl.validator(validateBalance),

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fcl.limit(500), // This will pass validation

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]);

Parameters

cb

• Type: Function
• Description: The validator function that takes an interaction and returns it (or throws an error if invalid)

Returns

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export type InteractionBuilderFn = (

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ix: Interaction,

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) => Interaction | Promise<Interaction>;

A function that processes an interaction object

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