Angular's @switch block has become a lot more useful recently. With exhaustive type checking, Angular can now catch missing template states when a TypeScript union or enum changes. And with grouped cases, we can remove duplicate markup when multiple states render the same UI. In this post, I'll show both improvements using a real-world example.
The Problem: UI States Can Drift from Your Types
Let's start with a common pattern.
We have a support queue where each ticket has a status:
There are four possible statuses, and we’re modeling them with a TypeScript union:
type TicketStatus =
| 'new'
| 'in-progress'
| 'resolved'
| 'closed';
interface Ticket {
id: number;
title: string;
customer: string;
status: TicketStatus;
}
Then, we have a signal containing a list of tickets:
protected readonly tickets = signal<Ticket[]>([
{
id: 1024,
title: 'User cannot reset password',
customer: 'Acme Corp',
status: 'new',
},
{
id: 1025,
title: 'Billing page shows incorrect total',
customer: 'Northstar Health',
status: 'in-progress',
},
{
id: 1026,
title: 'Exported report is missing rows',
customer: 'Velocity Labs',
status: 'resolved',
},
{
id: 1027,
title: 'Login button disabled after failed attempt',
customer: 'Summit Bank',
status: 'closed',
},
{
id: 1028,
title: 'Production checkout error for enterprise account',
customer: 'Atlas Retail',
status: 'new',
}
]);
So far, this is simple enough.
The status is strongly typed, and every ticket has to use one of the values from the TicketStatus union.
Now let's look at the template.
A Basic Angular @switch Block
In the template, we're looping over the tickets with @for and rendering each one as a card.
Inside each card, we use an Angular @switch block to render the status badge:
@switch (ticket.status) {
@case ('new') {
<span class="badge active">Active</span>
}
@case ('in-progress') {
<span class="badge active">Active</span>
}
@case ('resolved') {
<span class="badge done">Done</span>
}
@case ('closed') {
<span class="badge done">Done</span>
}
}
Then, a little lower in the card, we have another @switch block for the status message:
@switch (ticket.status) {
@case ('new') {
<p class="status-message active">
This ticket is new and needs to be triaged.
</p>
}
@case ('in-progress') {
<p class="status-message active">
Someone is actively working on this issue.
</p>
}
@case ('resolved') {
<p class="status-message done">
The issue has been resolved and is waiting for confirmation.
</p>
}
@case ('closed') {
<p class="status-message done">
This ticket is closed and no further action is needed.
</p>
}
}
This works, but there's a subtle problem.
Neither @switch block has a default case.
That means if the status ever becomes something other than these four values, Angular won't render anything for that part of the UI.
No badge.
No message.
Just a quiet little bug.
And those are the worst kind.
Adding a New Union Value
Now let's say the product changes.
We need to support urgent tickets, so we add a new status called "escalated":
type TicketStatus =
| 'new'
| 'in-progress'
| 'resolved'
| 'closed'
| 'escalated';
Then we update one of the tickets to use the new status:
{
id: 1028,
title: 'Production checkout error for enterprise account',
customer: 'Atlas Retail',
status: 'escalated',
}
TypeScript is happy.
The app still compiles.
And at first glance, everything looks fine.
But when the escalated ticket renders, the card is incomplete:
The ticket title and customer show up, but the badge and message are missing because neither @switch block handles the new value.
The type changed.
The data changed.
But the template didn't keep up.
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Exhaustive @switch Checking with @default never
This is where the newer @switch behavior helps.
Instead of adding a normal fallback UI, we can add this:
@default never;
This tells Angular that if the @switch reaches the default case, there should be no possible value left to handle.
So the badge @switch becomes this:
@switch (ticket.status) {
@case ('new') {
<span class="badge active">Active</span>
}
@case ('in-progress') {
<span class="badge active">Active</span>
}
@case ('resolved') {
<span class="badge done">Done</span>
}
@case ('closed') {
<span class="badge done">Done</span>
}
@default never;
}
Now Angular can type-check the @switch exhaustively.
Since TicketStatus includes escalated, but the template doesn't handle it yet, Angular reports an error:
That's the win.
Instead of silently rendering broken UI, Angular forces us to update the template when the union type changes.
This is especially useful for UI states like:
- ticket statuses
- order states
- payment states
- deployment states
- user invite states
- feature flag states
Any time a known set of values drives intentional UI, exhaustive checking is worth considering.
To fix the error, we just need to add the missing escalated case in both @switch blocks.
Cleaning Up Duplicate @case Blocks
Now that the @switch is safer, let's make it cleaner.
In the badge @switch, new and in-progress both render the same badge:
@case ('new') {
<span class="badge active">Active</span>
}
@case ('in-progress') {
<span class="badge active">Active</span>
}
And resolved and closed both render the same badge too:
@case ('resolved') {
<span class="badge done">Done</span>
}
@case ('closed') {
<span class="badge done">Done</span>
}
That duplication isn't terrible in a small example, but it gets annoying fast in real templates.
Modern Angular lets us combine consecutive cases that render the same block.
So we can rewrite the badge @switch like this:
@switch (ticket.status) {
@case ('new')
@case ('in-progress') {
<span class="badge active">Active</span>
}
@case ('resolved')
@case ('closed') {
<span class="badge done">Done</span>
}
@case ('escalated') {
<span class="badge escalated">Escalated</span>
}
@default never;
}
Angular treats those consecutive @case statements as multiple conditions for the same template block.
So new and in-progress both render the Active badge, while resolved and closed both render the Done badge.
We get the same UI, but without repeating the same markup in multiple cases.
Fewer places to forget something later.
Safer Templates, Cleaner Code
That’s the real upgrade.
The UI stays the same, but the template becomes safer, cleaner, and easier to maintain.
Exhaustive checking helps Angular catch missing states, and grouped cases help remove duplicate markup.
Small change, safer template.
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