How to check if a RxJS Observable contains a string in Angular2?

angular, rxjs, rxjs5, typescript

Solution

Observables are asynchronous so you can't use `let getRoles = ...map(...)`. The `map()` method is not executed on an array but on an Observable which is always asynchronous.

So proper way to do it could be (I didn't test this code):

public hasRole(name: string): Observable {
    return this.tokenService.getTokenInformation()
        .map(element => element.roles)
        .first(roles => roles.indexOf(name) !== -1);
}

Operator `first()` emits an error when no matching element was found when the source completed (when we iterated all roles).

Then use this method like:

hasRole('my-role').subscribe(
    role => console.log("has role"),
    error => console.log("doesn't have role"),
)

Edit:

This converts everything to only `true` or `false` values. See doc for `first()` operator what are these argument. Then I used `map()` to force convert everything into boolean.

public hasRole(name: string): Observable {
    return this.tokenService.getTokenInformation()
        .map(element => element.roles)
        .first(roles => roles.indexOf(name) !== -1, undefined, false)
        .map(val => !!val);
}

See live simplified demo: http://plnkr.co/edit/MtYfGLgqgHACPswFTVJ5

Problem

I am new to Angular2 and Observable, I want to check if a Observable `getRoles` which is of type `Observable<string[]>` contains a string. ``` public hasRole(name: string): boolean { // getRoles is of type Observable<string[]> let getRoles = this.tokenService.getTokenInformation().map(element => element.roles); if (/* check if name is inside of getRoles */) { return true; } return false; } ```

Original source