What's new in Angular 4.1?

Angular 4.1.0 is here!

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This will be a short blog post, because there are not a lot of new features…

The most part of the work has been done on the official docs, which are now an Angular CLI app, and this migration takes some time. We can then expect to have nice new content when this will be done.

So, what are the new features? Let’s dive in!


The internationalization module has a few bugfixes, and a notable new feature: the extracted messages file now has the source file for each message. It will be far easier for developers to know where the messages come from!

<trans-unit id="home.title" datatype="html">
  <source>Welcome to Ponyracer</source>
  <context-group purpose="location">
    <context context-type="sourcefile">src/app.component.ts</context>
    <context context-type="linenumber">10</context>


The main new feature of this release is the support of the brand new TypeScript 2.3 version, and the support of strictNullChecks.

This option allows to check if you won’t run into nullability problems in your app. Angular itself now has correct types. For example, when you try to retrieve a FormControl from a FormGroup with get, the returned type is AbstractControl | null.

That’s because the control you are trying to get might not exist, and, if you are not careful, you are introducing a bug in your application by supposing it does exist.

If you don’t have the strictNullChecks option, you can do:

static passwordMatch(control: FormGroup) {
  const password = control.get('password').value;

but when you enable it, the compiler will complain, and may save you by warning you that the control may not exist, and that your code should handle this case.

You have to do something like:

static passwordMatch(control: FormGroup) {
  const passwordCtrl = control.get('password');
  const password = passwordCtrl !== null ? passwordCtrl.value : '';

Or you can use the ! post-fix expression operator introduced by TypeScript, to basically say to the compiler “Shut up”:

static passwordMatch(control: FormGroup) {
  const password = control.get('password')!.value;

It can also be really interesting for your application models. Let’s say you have a UserModel representing your user, with a surname field that can be null. If you declare it correctly, the type should be:

interface UserModel {
  surname: string|null;

Then, with the strictNullChecks option activated, the compiler will help you when you use this model. For example:


will throw a warning as the surname field can be null.

When you have complex entities coming from your server, it can really help you to have this kind of warning to avoid subtle and hard to avoid bugs.

That’s all for this small release!

All our materials (ebook, online training (Pro Pack) and training) are up-to-date with these changes if you want to learn more!

Oh, and our Pro Pack has 3 new exercises about the router! A perfect way to learn about protecting routes with guards, nested routes, resolving data before displaying the component, and how to split your app in small chunks that can be lazy-loaded.

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