Angular Router by Savkin Victor

Author:Savkin, Victor [Savkin, Victor]
Language: eng
Format: azw3, pdf
Publisher: Packt Publishing
Published: 2017-03-20T04:00:00+00:00

Accessing snapshots

The router exposes parameters and data as observables, which is convenient most of the time, but not always. Sometimes what we want is a snapshot of the state that we can examine at once.

@Component({...}) class MessageCmp { constructor(r: ActivatedRoute) { r.url.subscribe(() => { r.snapshot; // any time url changes, this callback is fired }); } }

ActivatedRoute

The ActivatedRoute interface provides access to the url, params, data, queryParams, and fragment observables. We will look at each of them in detail, but first let's examine the relationships between them.

URL changes are the source of any changes in a route. And it has to be this way as the user has the ability to modify the location directly.

Any time the URL changes, the router derives a new set of parameters from it: the router takes the positional parameters (for example, :id) of the matched URL segments and the matrix parameters of the last matched URL segment and combines those. This operation is pure: the URL has to change for the parameters to change. Or in other words, the same URL will always result in the same set of parameters.

Next, the router invokes the route's data resolvers and combines the result with the provided static data. Since data resolvers are arbitrary functions, the router cannot guarantee that you will get the same object when given the same URL. Even more, often this cannot be the case! The URL contains the id of a resource, which is fixed, and data resolvers fetch the content of that resource, which often varies over time. Finally, the activated route provides the queryParams and fragment observables. In opposite to other observables, that are scoped to a particular route, query parameters and fragment are shared across multiple routes.

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