CASL React

This package allows to integrate @casl/ability with React application. It provides Can component that allow to hide or show UI elements based on user ability to see them.

@casl/react perfectly works with React Native

Installation

npm install @casl/react @casl/ability
# or
yarn add @casl/react @casl/ability
# or
pnpm add @casl/react @casl/ability

Can component

It accepts children and 6 properties:

• do - name of the action (e.g., read, update). Has an alias I

• on - checked subject. Has a, an, this aliases

• field - checked field

  export default ({ post }) => <Can I="read" this={post} field="title">
    Yes, you can do this! ;)
  </Can>

• not - inverts ability check and show UI if user cannot do some action:

  export default () => <Can not I="create" a="Post">
    You are not allowed to create a post
  </Can>

• passThrough - renders children in spite of what ability.can returns. This is useful for creating custom components based on Can. For example, if you need to disable button based on user permissions:

  export default () => (
    <Can I="create" a="Post" passThrough>
      {allowed => <button disabled={!allowed}>Save</button>}
    </Can>
  )

• ability - an instance of Ability which will be used to check permissions

• children - elements to hide or render. May be either a render function:

  export default () => <Can I="create" a="Post" ability={ability}>
    {() => <button onClick={this.createPost}>Create Post</button>}
  </Can>

  or React elements:

  export default () => <Can I="create" a="Post" ability={ability}>
    <button onClick={this.createPost}>Create Post</button>
  </Can>

it's better to pass children as a render function because it will not create additional React elements if user doesn't have ability to do some action (in the case above create Post)

Don't be scared by the amount of properties component takes, we will talk about how to bind some of them.

Bind Can to a particular Ability instance

It'd be inconvenient to pass ability in every Can component. That's why there are 2 function which allow to bind Can to use a particular instance of Ability:

• createCanBoundTo
  This function was created to support version of React < 16.4.0, those versions doesn't have Context API. Can be used like this:

  import { createCanBoundTo } from '@casl/react';
  import ability from './ability';
  
  export const Can = createCanBoundTo(ability);

• createContextualCan
  This function is created to support React's Context API and can be used like this:

  import { createContext } from 'react';
  import { createContextualCan } from '@casl/react';
  
  export const AbilityContext = createContext();
  export const Can = createContextualCan(AbilityContext.Consumer);

The 2 methods are almost the same, the 2nd one is slightly better because it will allow you to provide different Ability instances to different parts of your app and inject ability using contextType static property. Choose your way based on the version of React you use.

In this guide, we will use createContextualCan as it covers more cases in modern React development.

To finalize things, we need to provide an instance of Ability via AbilityContext.Provider:

import { AbilityContext } from './Can'
import ability from './ability'

export default function App({ props }) {
  return (
    <AbilityContext.Provider value={ability}>
      <TodoApp />
    </AbilityContext.Provider>
  )
}

See CASL guide to learn how to define Ability instance.

and use our Can component:

import React, { Component } from 'react'
import { Can } from './Can'

export class TodoApp extends Component {
  createTodo = () => {
    // implement logic to show new todo form
  };

  render() {
    return (
      <Can I="create" a="Todo">
        <button onClick={this.createTodo}>Create Todo</button>
      </Can>
    )
  }
}

Imperative access to Ability instance

Sometimes the logic in a component may be a bit complicated, so you can't use <Can> component. In such cases, you can use React's contextType component property:

import React, { Component } from 'react'
import { AbilityContext } from './Can'

export class TodoApp extends Component {
  createTodo = () => {
    // logic to show new todo form
  };

  render() {
    return (
      <div>
        {this.context.can('create', 'Todo') &&
          <button onClick={this.createTodo}>Create Todo</button>}
      </div>
    );
  }
}

TodoApp.contextType = AbilityContext;

or useContext hook:

import React, { useContext } from 'react';
import { AbilityContext } from './Can'

export default () => {
  const createTodo = () => { /* logic to show new todo form */ };
  const ability = useContext(AbilityContext);

  return (
    <div>
      {ability.can('create', 'Todo') &&
        <button onClick={createTodo}>Create Todo</button>}
    </div>
  );
}

In that case, you need to create a new Ability instance when you want to update user permissions (don't use update method, it won't trigger re-rendering in this case) or you need to force re-render the whole app.

To make things easier, @casl/react provides useAbility hook that accepts React.Context as the only argument (the same as useContext), but triggers re-render in the component where you use this hook when you update Ability rules. The example above can be rewritten to:

import { useAbility } from '@casl/react';
import { AbilityContext } from './Can'

export default () => {
  const createTodo = () => { /* logic to show new todo form */ };
  const ability = useAbility(AbilityContext);

  return (
    <div>
      {ability.can('create', 'Todo') &&
        <button onClick={createTodo}>Create Todo</button>}
    </div>
  );
}

Usage note on React < 16.4 with TypeScript

If you use TypeScript and React < 16.4 make sure to add @casl/react/contextAPIPatch.d.ts file in your tscofig.json, otherwise your app won't compile:

{
  // other configuration options
  "include": [
    "src/**/*",
    "@casl/react/contextAPIPatch.d.ts" // <-- add this line
  ]
}

Property names and aliases

As you can see from the code above, component name and its property names and values create an English sentence, actually a question. For example, the code below reads as Can I create a Post:

export default () => <Can I="create" a="Post">
  <button onClick={...}>Create Post</button>
</Can>

There are several other property aliases which allow to construct a readable question:

• use a (or an) alias when you check by Type

  export default () => <Can I="read" a="Post">...</Can>

• use this alias instead of a when you check action on a particular instance. So, the question can be read as "Can I read this particular post?"

  // `this.props.post` is an instance of `Post` class (i.e., model instance)
  export default () => <Can I="read" this={this.props.post}>...</Can>

• use do and on if you are bored and don't want to make your code more readable ;)

  // `this.props.post` is an instance of `Post` class (i.e., model instance)
  export default () => <Can do="read" on={this.props.post}>...</Can>
  
  // or per field check
  export default () => <Can do="read" on={this.props.post} field="title">...</Can>

TypeScript support

The package is written in TypeScript, so don't worry that you need to keep all the properties and aliases in mind. If you use TypeScript, your IDE will suggest you the correct usage and TypeScript will warn you if you make a mistake.

Update Ability instance

Majority of applications that need permission checking support have something like AuthService or LoginService or Session service (name it as you wish) which is responsible for user login/logout functionality. Whenever user login (and logout), we need to update Ability instance with new rules. Usually you will do this in your LoginComponent.

Let's imagine that server returns user with a role on login:

import { AbilityBuilder, Ability } from '@casl/ability';
import React, { useState, useContext } from 'react';
import { AbilityContext } from './Can';

function updateAbility(ability, user) {
  const { can, rules } = new AbilityBuilder(Ability);

  if (user.role === 'admin') {
    can('manage', 'all');
  } else {
    can('read', 'all');
  }

  ability.update(rules);
}

export default () => {
  const [username, setUsername] = useState('');
  const [password, setPassword] = useState('');
  const ability = useContext(AbilityContext);
  const login = () => {
    const params = {
      method: 'POST',
      body: JSON.stringify({ username, password })
    };
    return fetch('path/to/api/login', params)
      .then(response => response.json())
      .then(({ user }) => updateAbility(ability, user));
  };

  return (
    <form>
      {/* input fields */}
      <button onClick={login}>Login</button>
    </form>
  );
};

See Define rules to get more information of how to define Ability

Want to help?

Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on guidelines for contributing.

If you'd like to help us sustain our community and project, consider to become a financial contributor on Open Collective

See Support CASL for details

License

MIT License