@dfinity/agent
v2.1.3
Published
JavaScript and TypeScript library to interact with the Internet Computer
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@dfinity/agent
JavaScript and TypeScript library to interact with the Internet Computer for Node.js and Client applications
Visit the Dfinity Forum and SDK Documentation for more information and support building on the Internet Computer.
Additional API Documentation can be found here.
Installation
Using agent:
npm i --save @dfinity/agent
In the browser:
import * as agent from "@dfinity/agent";
or using individual exports:
import { Actor, HttpAgent } from '@dfinity/agent';
In Node.js
const DfinityAgent = require('@dfinity/agent');
or using individual exports:
const { Actor, HttpAgent } = require('@dfinity/agent');
Using an Agent
The agent is a low-level interface that the Actor uses to encode and decode messages to the Internet Computer. It provides call
, query
and readState
methods to the Actor, as well as a few additional utilities. For the most part, calls through the agent are intended to be structured through an Actor, configured with a canister interface that can be automatically generated from a Candid interface.
Initializing an Actor
The most common use for the agent is to create an actor. This is done by calling the Actor.createActor
constructor:
Actor.createActor(interfaceFactory: InterfaceFactory, configuration: ActorConfig): ActorSubclass<T>
The interfaceFactory
is a function that returns a runtime interface that the Actor uses to strucure calls to a canister. The interfaceFactory can be written manually, but it is recommended to use the dfx generate
command to generate the interface for your project, or to use the didc
tool to generate the interface for your project.
Actors can also be initialized to include the boundary node http headers, This is done by calling the Actor.createActor
constructor:
Actor.createActorWithHttpDetails(interfaceFactory: InterfaceFactory, configuration: ActorConfig): ActorSubclass<ActorMethodMappedWithHttpDetails<T>>
Inspecting an actor's agent
Use the Actor.agentOf
method to get the agent of an actor:
const defaultAgent = Actor.agentOf(defaultActor);
This is useful if you need to replace or invalidate the identity used by an actor's agent.
For example, if you want to replace the identity of an actor's agent with a newly authenticated identity from Internet Identity, you can do so by calling the Actor.replaceAgent
method:
defaultAgent.replaceIdentity(await authClient.getIdentity());
Tips for using fetch
The agent uses the browser fetch
API to make calls to the Internet Computer. If you are not using the agent in the browser, you can pass a custom fetch
implementation to the agent's constructor. This is useful if you want to use a custom fetch implementation, such as one that adds authentication headers to the request. We recommend using the isomorphic-fetch package to provide a consistent fetch API across Node.js and the browser. You will also need to provide a host
option to the agent's constructor, as the agent will not be able to determine the host from the global context.
For example,
import fetch from 'isomorphic-fetch';
import { HttpAgent } from '@dfinity/agent';
const host = process.env.DFX_NETWORK === 'local' ? 'http://127.0.0.1:4943' : 'https://icp-api.io';
const agent = new HttpAgent({ fetch, host });
You can also pass fetchOptions
to the agent's constructor, which will be passed to the fetch
implementation. This is useful if you want to pass additional options to the fetch
implementation, such as a custom header.
For example,
import fetch from 'isomorphic-fetch';
import { HttpAgent } from '@dfinity/agent';
const host = process.env.DFX_NETWORK === 'local' ? 'http://127.0.0.1:4943' : 'https://ic0.app';
/**
* @type {RequestInit}
*/
const fetchOptions = {
headers: {
'X-Custom-Header': 'value',
},
};
const agent = new HttpAgent({ fetch, host, fetchOptions });