I want to execute some logic in my Angular component when a certain event occurs in the Signal Store. This event could be:

A specific signal changing.

Fetching data using an rxMethod (RxJS), which eventually updates a signal.

Since my store does not have direct access to the component, I need a way to react when a signal changes.

A common use case:

After an update operation, I want to clear a form or update a FormControl when a signal changes.

Potential Approaches: Use effect inside the component – However, Angular does not recommend this in its documentation.

Pass a callback function to the store and trigger it when data is fetched.

Question: Is there a recommended best practice for this use case? How should I react to store updates inside my component in an idiomatic Angular way?

I want to execute some logic in my Angular component when a certain event occurs in the Signal Store. This event could be:

A specific signal changing.

Fetching data using an rxMethod (RxJS), which eventually updates a signal.

Since my store does not have direct access to the component, I need a way to react when a signal changes.

A common use case:

After an update operation, I want to clear a form or update a FormControl when a signal changes.

Potential Approaches: Use effect inside the component – However, Angular does not recommend this in its documentation.

Pass a callback function to the store and trigger it when data is fetched.

Question: Is there a recommended best practice for this use case? How should I react to store updates inside my component in an idiomatic Angular way?

• angular
• ngrx-signal-store

1 Answer 1

You can use a linked signal for this

Let’s consider an example: Suppose we have a signal that represents the amount of money in a user’s account:

const accountBalance = signal(1000);

Now, let's create a signal that will automatically convert this value to euros:

const accountBalanceInEuros = linkedSignal(() => accountBalance() / 1.12);

The result when changing the main signal is the same, the linked one will change automatically.

There are situations where you need more flexible settings. The linkedSignal allows you to pass an object that defines the update logic:

selectedProduct = signal('Laptop');
priceSignal = linkedSignal({
    source: () => this.selectedProduct(), // Base signal (source)
    computation: (product, previous) => {
      if (previous?.source === product && previous?.value) {
        // If the product hasn't changed, use the previous value
        return previous.value;
      }
      // Fetch the price from an API when the product changes
      return this.fetchPrice(product);
    },
    equal: (newVal, oldVal) => newVal.price === oldVal.price
    // equal prevents unnecessary updates if the price remains the same
  });

This approach allows you to create a linked signal that automatically updates only if the price of the selected product changes, minimizing unnecessary re-renders.