Signals as modern state primitive in Angular - Step-by-Step Execution

Concept Flow - Signals as modern state primitive

Create signal with initial value

↓

Read signal value in template or code

↓

Update signal value with set()

↓

Signal notifies dependents

↓

UI or computed values re-evaluate

↓

User sees updated UI

Signals hold state and notify Angular when their value changes, triggering UI updates automatically.

Execution Sample

Angular

import { signal } from '@angular/core';

const count = signal(0);

count.set(1);
console.log(count());

This code creates a signal holding 0, updates it to 1, then logs the current value.

Execution Table

Step	Action	Signal Value Before	Signal Value After	Effect
1	Create signal with initial value 0	N/A	0	Signal initialized
2	Read signal value with count()	0	0	Returns current value 0
3	Update signal value with count.set(1)	0	1	Signal value updated, dependents notified
4	Read signal value again with count()	1	1	Returns updated value 1

💡 No more actions; signal holds value 1 and UI would update accordingly

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
count	undefined	0	1	1

Key Moments - 3 Insights

Why do we call count() to read the signal value instead of accessing a property?

Signals are functions in Angular; calling count() returns the current value as shown in execution_table step 2 and 4.

What happens when we call count.set(1)? Does it immediately update the UI?

Calling set(1) updates the signal value and notifies dependents (step 3). Angular then schedules UI updates automatically.

Can we directly assign a new value to count like count = 2?

No, count is a signal function, not a variable. Use count.set(2) to update the value as shown in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the signal value after step 3?

A 0

B 1

C undefined

D 2

💡 Hint

Check the 'Signal Value After' column for step 3 in the execution_table.

At which step does the signal notify dependents about the value change?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Effect' column mentioning dependents notification in the execution_table.

If we replace count.set(1) with count.set(5), what changes in the variable_tracker?

A The final value of count becomes 5

B The start value changes to 5

C The value after step 1 changes to 5

D No change in variable_tracker

💡 Hint

Variable tracker shows signal value changes after set() calls; changing set value updates final.

Concept Snapshot

Signals are functions holding state in Angular.
Create with signal(initialValue).
Read value by calling signal(), e.g. count().
Update with signal.set(newValue).
Updates notify Angular to refresh UI automatically.

Full Transcript

Signals in Angular are a modern way to hold and manage state. You create a signal with an initial value using signal(). To read the current value, you call the signal as a function, like count(). To update the value, you use count.set(newValue). When the value changes, Angular automatically updates the UI where the signal is used. This makes state management simple and reactive without complex code.