buildMessageHandler

Creates a message handler for processing window messages from wallet service frames or popups. This handler manages the communication protocol between FCL and wallet services, including ready states, responses, and cleanup operations.

Import

You can import the entire package and access the function:

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import * as fcl from "@onflow/fcl-core"

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fcl.buildMessageHandler(buildMessageHandlerParams)

Or import directly the specific function:

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import { buildMessageHandler } from "@onflow/fcl-core"

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buildMessageHandler(buildMessageHandlerParams)

Usage

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// Create a message handler for wallet communication

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const handler = buildMessageHandler({

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close: () => cleanup(),

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send: (msg) => postMessage(msg),

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onReady: (e, utils) => initializeWallet(utils),

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onResponse: (e, utils) => handleResponse(e.data),

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onMessage: (e, utils) => processMessage(e),

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onCustomRpc: (payload, utils) => handleRpc(payload)

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})

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window.addEventListener("message", handler)

Parameters

buildMessageHandlerParams

• Type:

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export interface BuildMessageHandlerParams {

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close: () => void

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send: (msg: any) => void

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onReady: (

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e: MessageEvent,

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utils: {send: (msg: any) => void; close: () => void}

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) => void

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onResponse: (

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e: MessageEvent,

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utils: {send: (msg: any) => void; close: () => void}

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) => void

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onMessage: (

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e: MessageEvent,

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utils: {send: (msg: any) => void; close: () => void}

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) => void

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onCustomRpc: (

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payload: any,

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utils: {send: (msg: any) => void; close: () => void}

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) => void

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getSource?: () => Window | null

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}

Returns

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(e: MessageEvent<any>) => void

Message event handler function that can be attached to window message listeners

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