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ContextView

The ContextView class allows you to track a set of bindings that match a specific filter. It provides methods for resolving and observing these bindings.

Constructor​

constructor​

Creates a new ContextView instance.

Parameters:

  • context: The Context to view.
  • filter: A function that filters bindings.
  • comparator (optional): A function that compares bindings for sorting.

Returns: A new ContextView instance.

Example:

// Create a view that tracks all bindings with the 'service' tag
const serviceView = new ContextView<any>(
  context,
  binding => binding.tags.has('service'),
  (a, b) => a.key.localeCompare(b.key)
);

Methods​

resolve​

Resolves all bindings that match the filter.

Returns: A Promise that resolves to an array of resolved values.

Example:

// Resolve all services
const services = await serviceView.resolve();
console.log(`Resolved ${services.length} services`);

values​

Alias for resolve(). Resolves all bindings that match the filter.

Returns: A Promise that resolves to an array of resolved values.

Example:

// Resolve all services
const services = await serviceView.values();
console.log(`Resolved ${services.length} services`);

bindings​

Gets all bindings that match the filter.

Returns: An array of bindings.

Example:

// Get all service bindings
const bindings = serviceView.bindings();
console.log(`Found ${bindings.length} service bindings`);

Event Methods​

on​

Adds an event listener for the given event.

Parameters:

  • event: The event name.
  • listener: The event listener function.

Returns: The ContextView instance (for method chaining).

Example:

// Listen for binding changes
serviceView.on('bind', (binding) => {
  console.log(`New service binding: ${binding.key}`);
});

once​

Adds a one-time event listener for the given event.

Parameters:

  • event: The event name.
  • listener: The event listener function.

Returns: The ContextView instance (for method chaining).

Example:

// Listen for the next binding change only
serviceView.once('bind', (binding) => {
  console.log(`New service binding: ${binding.key}`);
});

off​

Removes an event listener for the given event.

Parameters:

  • event: The event name.
  • listener: The event listener function to remove.

Returns: The ContextView instance (for method chaining).

Example:

// Create a listener
const listener = (binding) => {
  console.log(`New service binding: ${binding.key}`);
};

// Add the listener
serviceView.on('bind', listener);

// Later, remove the listener
serviceView.off('bind', listener);

Lifecycle Methods​

close​

Closes the ContextView, removing all event listeners.

Example:

// Close the view when done
serviceView.close();

Events​

The ContextView class emits the following events:

  • bind: Emitted when a binding that matches the filter is added to the context.
  • unbind: Emitted when a binding that matches the filter is removed from the context.

Complete Example​

Here's a complete example showing how to use the ContextView class:

import { Context, ContextView, injectable } from 'contexify';

// Create a context
const context = new Context('application');

// Define some services
@injectable()
class LoggerService {
  log(message: string) {
    console.log(`[LOG] ${message}`);
  }
}

@injectable()
class UserService {
  getUsers() {
    return ['user1', 'user2', 'user3'];
  }
}

@injectable()
class OrderService {
  getOrders() {
    return ['order1', 'order2'];
  }
}

// Bind the services to the context
context.bind('services.LoggerService').toClass(LoggerService).tag('service');
context.bind('services.UserService').toClass(UserService).tag('service');
context.bind('services.OrderService').toClass(OrderService).tag('service');

// Create a view of all services
const serviceView = new ContextView<any>(
  context,
  binding => binding.tags.has('service'),
  (a, b) => a.key.localeCompare(b.key)
);

// Listen for new services
serviceView.on('bind', (binding) => {
  console.log(`New service detected: ${binding.key}`);
});

// Use the view
async function run() {
  // Get all service bindings
  const bindings = serviceView.bindings();
  console.log(`Found ${bindings.length} service bindings:`);
  bindings.forEach(binding => console.log(`- ${binding.key}`));

  // Resolve all services
  const services = await serviceView.resolve();
  console.log(`Resolved ${services.length} services`);

  // Add a new service
  context.bind('services.PaymentService').toClass(PaymentService).tag('service');

  // Close the view when done
  serviceView.close();
}

run().catch(err => console.error(err));