Flow Interaction Templates (FLIX)

info

For Cadence 0.42 go to Legacy Docs

FLIX helps developers reuse existing Cadence transactions and scripts to easily integrate with existing Cadence smart contracts. Get more information about Flow Interaction Templates

Introduction

The Flow CLI provides a flix command with a few sub commands execute and package. Get familiar with Flow Interaction Templates (FLIX). FLIX are a standard for distributing Cadence scripts and transactions, and metadata in a way that is consumable by tooling and wallets. FLIX can be audited for correctness and safety by auditors in the ecosystem.

>flow flix
execute, generate, package
Usage:
  flow flix [command]
Available Commands:
  execute     execute FLIX template with a given id, name, local filename, or url
  generate    generate FLIX json template given local Cadence filename
  package     package file for FLIX template fcl-js is default

Execute

The Flow CLI provides a flix command to execute FLIX. The Cadence being execute in the FLIX can be a transaction or script.

flow flix execute <query> [<argument> <argument>...] [flags]

warning

A FLIX template might only support testnet and/or mainnet. Generally, emulator is not supported. This can be the case if the FLIX template relies on contract dependencies.

Queries can be a FLIX id, name, url or path to a local FLIX file.

Execute Usage

# Execute a FLIX transaction by name on Testnet
flow flix execute transfer-flow 5.0 "0x123" --network testnet --signer "testnet-account"

# Execute a FLIX script by id on Testnet
flow flix execute bd10ab0bf472e6b58ecc0398e9b3d1bd58a4205f14a7099c52c0640d9589295f --network testnet

# Execute a local FLIX script by path on Testnet
flow flix execute ./multiply.template.json 2 3 --network testnet

The Flow CLI provides a flix command to package up generated plain and simple JavaScript. This JavaScript uses FCL (Flow Client Library) to call the cadence the Flow Interaction Templates (FLIX) is based on.

info

Currently, flix package command only supports generating FCL (Flow Client Library) specific JavaScript and TypeScirpt, there are plans to support other languages like golang.

flow flix package <query> [flags]

Generate

Generate FLIX json file. This command will take in a Cadence file and produce a FLIX json file. There are two ways to provide metadata to populate the FLIX json structure.

Use --pre-fill flag to pass in a pre populated FLIX json structure

warning

When generating a FLIX template, make sure all contract dependencies have been deployed to the supported networks. Add any aliases to your flow.json that will be needed to populate dependencies. Verify all dependencies have been populated after generating.

Generate Usage

# Generate FLIX json file using cadence transaction or script, this example is not using a prefilled json file so will not have associated message metadata 
flow flix generate cadence/transactions/update-helloworld.cdc --save cadence/templates/update-helloworld.template.json

Example of Cadence simple, no metadata associated

import "HelloWorld"
pub fun main(): String {
  return HelloWorld.greeting
}

Cadence Doc Pragma:

It's recommended to use pragma to set the metadata for the script or transaction. More information on Cadence Doc Pragma FLIP

A pragma is short for "pragmatic information", it's special instructions to convey information to a processor in this case the utility that generates FLIX.

import "HelloWorld"
#interaction (
    version: "1.1.0",
    title: "Update Greeting",
    description: "Update the greeting on the HelloWorld contract",
    language: "en-US",
)
transaction(greeting: String) {
  prepare(acct: AuthAccount) {
    log(acct.address)
  }
  execute {
    HelloWorld.updateGreeting(newGreeting: greeting)
  }
}

info

Cadence v0.42.7 supports additional Cadence pragma functionality that FlIX utility can use to generate FLIX. It will support parameters "title" and "description".

The resulting json metadata is extracted from Cadence Doc Pragma

{
    "f_type": "InteractionTemplate",
    "f_version": "1.1.0",
    "id": "",
    "data": {
        "type": "transaction",
        "interface": "",
        "messages": [
            {
                "key": "title",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Update Greeting"
                    }
                ]
            },
            {
                "key": "description",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Update the greeting on the HelloWorld contract"
                    }
                ]
            }
        ],
        "cadence": {},
        "dependencies": [],
         "parameters": [
            {
                "label": "greeting",
                "index": 0,
                "type": "String",
                "messages": []
            }
        ]
    }
}

Example of using a prefilled FLIX json file. No need to use Cadence pragma when using a prefilled FLIX json file. This method separates FLIX specific information from the transaction or script Cadence. Use the flow flix generate command:

flow flix generate cadence/scripts/read-helloworld.cdc --pre-fill cadence/templates/read-helloworld.prefill.json --save cadence/templates/read-helloworld.template.json

Using a pre-filled FLIX template, the cadence can be simple but no metadata accompanies it.

import "HelloWorld"
pub fun main(): String {
  return HelloWorld.greeting
}

Example of json prefill file with message metadata:

{
    "f_type": "InteractionTemplate",
    "f_version": "1.1.0",
    "id": "",
    "data": {
        "type": "script",
        "interface": "",
        "messages": [
            {
                "key": "title",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Get Greeting"
                    }
                ]
            },
            {
                "key": "description",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Call HelloWorld contract to get greeting"
                    }
                ]
            }
        ]
    }
}

The resulting FLIX json file after generation:

{
    "f_type": "InteractionTemplate",
    "f_version": "1.1.0",
    "id": "fd9abd34f51741401473eb1cf676b105fed28b50b86220a1619e50d4f80b0be1",
    "data": {
        "type": "script",
        "interface": "",
        "messages": [
            {
                "key": "title",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Get Greeting"
                    }
                ]
            },
            {
                "key": "description",
                "i18n": [
                    {
                        "tag": "en-US",
                        "translation": "Call HelloWorld contract to get greeting"
                    }
                ]
            }
        ],
        "cadence": {
            "body": "import \"HelloWorld\"\npub fun main(): String {\n  return HelloWorld.greeting\n}\n",
            "network_pins": [
                {
                    "network": "testnet",
                    "pin_self": "41c4c25562d467c534dc92baba92e0c9ab207628731ee4eb4e883425abda692c"
                }
            ]
        },
        "dependencies": [
            {
                "contracts": [
                    {
                        "contract": "HelloWorld",
                        "networks": [
                            {
                                "network": "testnet",
                                "address": "0xe15193734357cf5c",
                                "dependency_pin_block_height": 137864533,
                                "dependency_pin": {
                                    "pin": "aad46badcab3caaeb4f0435625f43e15bb4c15b1d55c74a89e6f04850c745858",
                                    "pin_self": "a06b3cd29330a3c22df3ac2383653e89c249c5e773fd4bbee73c45ea10294b97",
                                    "pin_contract_name": "HelloWorld",
                                    "pin_contract_address": "0xe15193734357cf5c",
                                    "imports": []
                                }
                            }
                        ]
                    }
                ]
            }
        ],
        "parameters": null
    }
}

Package

Queries can be a FLIX url or path to a local FLIX file. This command leverages FCL which will execute FLIX cadence code. Package files can be generated in JavaScript or TypeScript.

warning

Currently package doesn't support id, name flix query.

Package Usage

# Generate packaged code that leverages FCL to call the Cadence transaction code, `--save` flag will save the output to a specific file
flow flix package transfer-flow --save ./package/transfer-flow.js

# Generate package code for a FLIX script using id, since there is no saving file, the result will display in terminal
flow flix package bd10ab0bf472e6b58ecc0398e9b3d1bd58a4205f14a7099c52c0640d9589295f

# Generate package code using local template file to save in a local file 
flow flix package ./multiply.template.json --save ./multiply.js

# Generate package code using local template file to save in a local typescript file 
flow flix package ./multiply.template.json --lang ts --save ./multiply.ts

Example Package Output

flow flix package https://flix.flow.com/v1/templates\?name\=transfer-flow

/**
    This binding file was auto generated based on FLIX template v1.0.0. 
    Changes to this file might get overwritten.
    Note fcl version 1.3.0 or higher is required to use templates. 
**/
import * as fcl from "@onflow/fcl"
const flixTemplate = "https://flix.flow.com/v1/templates?name=transfer-flow"
/**
* Transfer tokens from one account to another
* @param {Object} Parameters - parameters for the cadence
* @param {string} Parameters.amount - The amount of FLOW tokens to send: UFix64
* @param {string} Parameters.to - The Flow account the tokens will go to: Address
* @returns {Promise<string>} - returns a promise which resolves to the transaction id
*/
export async function transferTokens({amount, to}) {
  const transactionId = await fcl.mutate({
    template: flixTemplate,
    args: (arg, t) => [arg(amount, t.UFix64), arg(to, t.Address)]
  });
  return transactionId
}

# Generate TypeScript version of package file 
flow flix package https://flix.flow.com/v1/templates?name=transfer-flow --lang ts

/**
    This binding file was auto generated based on FLIX template v1.1.0. 
    Changes to this file might get overwritten.
    Note fcl version 1.9.0 or higher is required to use templates. 
**/
import * as fcl from "@onflow/fcl"
const flixTemplate = "https://flix.flow.com/v1/templates?name=transfer-flow"
interface TransferTokensParams {
  amount: string; // The amount of FLOW tokens to send
  to: string; // The Flow account the tokens will go to
}
/**
* transferTokens: Transfer tokens from one account to another
* @param string amount - The amount of FLOW tokens to send
* @param string to - The Flow account the tokens will go to
* @returns {Promise<string>} - Returns a promise that resolves to the transaction ID
*/
export async function transferTokens({amount, to}: TransferTokensParams): Promise<string> {
  const transactionId = await fcl.mutate({
    template: flixTemplate,
    args: (arg, t) => [arg(amount, t.UFix64), arg(to, t.Address)]
  });
  return transactionId
}

warning

Notice that fcl v1.9.0 is needed to use FLIX v1.1 templates

Resources

To find out more about FLIX, see the read the FLIP.

For a list of all templates, check out the FLIX template repository.

To generate a FLIX, see the FLIX CLI readme.

Arguments

Name: argument
Valid input: valid FLIX

Input argument value matching corresponding types in the source code and passed in the same order. You can pass a nil value to optional arguments by executing the flow FLIX execute script like this: flow flix execute template.json nil.

Flags

Arguments JSON

Flag: --args-json
Valid inputs: arguments in JSON-Cadence form.
Example: flow flix execute template.script.json '[{"type": "String", "value": "Hello World"}]'

Arguments passed to the Cadence script in the Cadence JSON format. Cadence JSON format contains type and value keys and is documented here.

Pre Fill

Flag: --pre-fill
Valid inputs: a json file in the FLIX json structure FLIX json format

Block Height

Flag: --block-height
Valid inputs: a block height number

Block ID

Flag: --block-id
Valid inputs: a block ID

Signer

Flag: --signer
Valid inputs: the name of an account defined in the configuration (flow.json)

Specify the name of the account that will be used to sign the transaction.

Proposer

Flag: --proposer
Valid inputs: the name of an account defined in the configuration (flow.json)

Specify the name of the account that will be used as proposer in the transaction.

Payer

Flag: --payer
Valid inputs: the name of an account defined in the configuration (flow.json)

Specify the name of the account that will be used as payer in the transaction.

Authorizer

Flag: --authorizer
Valid inputs: the name of a single or multiple comma-separated accounts defined in the configuration (flow.json)

Specify the name of the account(s) that will be used as authorizer(s) in the transaction. If you want to provide multiple authorizers separate them using commas (e.g. alice,bob)

Gas Limit

Flag: --gas-limit
Valid inputs: an integer greater than zero.
Default: 1000

Specify the gas limit for this transaction.

Host

Flag: --host
Valid inputs: an IP address or hostname.
Default: 127.0.0.1:3569 (Flow Emulator)

Specify the hostname of the Access API that will be used to execute the command. This flag overrides any host defined by the --network flag.

Network Key

Flag: --network-key
Valid inputs: A valid network public key of the host in hex string format

Specify the network public key of the Access API that will be used to create a secure GRPC client when executing the command.

Network

Flag: --network
Short Flag: -n
Valid inputs: the name of a network defined in the configuration (flow.json)
Default: emulator

Specify which network you want the command to use for execution.

Filter

Flag: --filter
Short Flag: -x
Valid inputs: a case-sensitive name of the result property.

Specify any property name from the result you want to return as the only value.

Output

Flag: --output
Short Flag: -o
Valid inputs: json, inline

Specify the format of the command results.

Save

Flag: --save
Short Flag: -s
Valid inputs: a path in the current filesystem.

Specify the filename where you want the result to be saved

Log

Flag: --log
Short Flag: -l
Valid inputs: none, error, debug
Default: info

Specify the log level. Control how much output you want to see during command execution.

Configuration

Flag: --config-path
Short Flag: -f
Valid inputs: a path in the current filesystem.
Default: flow.json

Specify the path to the flow.json configuration file. You can use the -f flag multiple times to merge several configuration files.

Version Check

Flag: --skip-version-check
Default: false

Skip version check during start up to speed up process for slow connections.

Introduction​

Execute​

Execute Usage​

Generate​

Generate Usage​

Cadence Doc Pragma:​

Package​

Package Usage​

Example Package Output​

Resources​

Arguments​

Flags​

Arguments JSON​

Pre Fill​

Block Height​

Block ID​

Signer​

Proposer​

Payer​

Authorizer​

Gas Limit​

Host​

Network Key​

Network​

Filter​

Output​

Save​

Log​

Configuration​

Version Check​

Introduction

Execute

Execute Usage

Generate

Generate Usage

Cadence Doc Pragma:

Package

Package Usage

Example Package Output

Resources

Arguments

Flags

Arguments JSON

Pre Fill

Block Height

Block ID

Signer

Proposer

Payer

Authorizer

Gas Limit

Host

Network Key

Network

Filter

Output

Save

Log

Configuration

Version Check