withContext

The withContext method updates the context of the Guantr instance and removes the withContext method from the new instance. This allows setting a specific context for the instance which can be used in permission conditions.

Usage

Import and Define Context

First, import the necessary types and define the context:

import { createGuantr, GuantrMeta, GuantrCondition } from 'guantr';

type Context = {
  user: {
    id: number;
    role: string;
  };
};

type ResourceMap = {
  post: {
    action: 'create' | 'read' | 'update' | 'delete';
    model: {
      id: number;
      title: string;
      published: boolean;
      authorId: number;
    };
  };
};

Create Guantr Instance with Context

const guantr = createGuantr<GuantrMeta<ResourceMap>>().withContext<Context>({
  user: {
    id: 1,
    role: 'admin'
  }
});

Define Contextual Permissions

Define permissions that use the context to conditionally allow or deny actions:

// Define contextual permissions
guantr.setPermission((can, cannot) => {
  can('read', 'post');
  cannot('update', ['post', { authorId: ['equals', 'context.user.id'] }]);
});

Check Permissions with Context

Check permissions while considering the context:

// Check permissions with context
const canUpdateOwnPost = guantr.can('update', ['post', { id: 1, authorId: 1, title: 'My Post' }]); // false
const canUpdateOtherPost = guantr.can('update', ['post', { id: 2, authorId: 2, title: 'Other Post' }]); // true

In this example, the context is used to restrict users from updating posts that they do not own. The ContextField utility is leveraged to reference fields within the context object, ensuring that permissions are dynamically evaluated based on the current context.

References

Signature

withContext<T extends Context>(context: T): Omit<Guantr<Meta, T>, 'withContext'>;

Parameters

• context (Record<string, any>): The new context to set.

Returns

• Omit<Guantr<Meta, T>, 'withContext'>: A new instance of Guantr with the updated context, excluding the withContext method.