The Router use the type `Params` for all of:
- position parameters,
- matrix parameters,
- query parameters.
`Params` is defined as follow `type Params = {[key: string]: any}`
Because parameters can either have single or multiple values, the type should
actually be `type Params = {[key: string]: string | string[]}`.
The client code often assumes that parameters have single values, as in the
following exemple:
```
class MyComponent {
sessionId: Observable<string>;
constructor(private route: ActivatedRoute) {}
ngOnInit() {
this.sessionId = this.route
.queryParams
.map(params => params['session_id'] || 'None');
}
}
```
The problem here is that `params['session_id']` could be `string` or `string[]`
but the error is not caught at build time because of the `any` type.
Fixing the type as describe above would break the build because `sessionId`
would becomes an `Observable<string | string[]>`.
However the client code knows if it expects a single or multiple values. By
using the new `ParamMap` interface the user code can decide when it needs a
single value (calling `ParamMap.get(): string`) or multiple values (calling
`ParamMap.getAll(): string[]`).
The above exemple should be rewritten as:
```
class MyComponent {
sessionId: Observable<string>;
constructor(private route: ActivatedRoute) {}
ngOnInit() {
this.sessionId = this.route
.queryParamMap
.map(paramMap => paramMap.get('session_id') || 'None');
}
}
```
Added APIs:
- `interface ParamMap`,
- `ActivatedRoute.paramMap: ParamMap`,
- `ActivatedRoute.queryParamMap: ParamMap`,
- `ActivatedRouteSnapshot.paramMap: ParamMap`,
- `ActivatedRouteSnapshot.queryParamMap: ParamMap`,
- `UrlSegment.parameterMap: ParamMap`
This contains major changes to the compiler, bootstrap of the platforms
and test environment initialization.
Main part of #10043Closes#10164
BREAKING CHANGE:
- Semantics and name of `@AppModule` (now `@NgModule`) changed quite a bit.
This is actually not breaking as `@AppModules` were not part of rc.4.
We will have detailed docs on `@NgModule` separately.
- `coreLoadAndBootstrap` and `coreBootstrap` can't be used any more (without migration support).
Use `bootstrapModule` / `bootstrapModuleFactory` instead.
- All Components listed in routes have to be part of the `declarations` of an NgModule.
Either directly on the bootstrap module / lazy loaded module, or in an NgModule imported by them.
