Angular: map string array to array of enum values in http get call

Question

I have an enumeration in my typescript code, which lists all possible user roles:

enum UserRole {
    CONSULTANT,
    MANAGER,
    ...
}

And I have a REST endpoint /users/id/roles that returns array of strings representing roles of a particular user:

[
    "CONSULTANT",
    "MANAGER",
    ...
]

Now I want to map this array in my frontend code. I tied doing it like this:

import {Http} from '@angular/http';
import {Observable} from "rxjs/Observable";
import {plainToClass} from "class-transformer";
...

getUserRoles(id: string): Observable<UserRole[]> {
    return this.http.get(`/users/${id}/roles`)
        .map(responce => plainToClass(UserRole, responce.json()));
}

But I get:

error TS2345: Argument of type 'typeof UserRole' is not assignable to parameter of type 'ClassType'. Type 'typeof UserRole' provides no match for the signature 'new (...args: any[]): UserRole[]'.

Q: Is there any way to convert string-array to array of enum elements?

Note: Im using Typescript 2.5.3. in pair with Angular 5.0.5.

Kirk Larkin · Accepted Answer · 2017-12-12 16:09:42Z

4

You can use map on the array returned from your server, once you've converted it to an object using json, like so:

return this.http.get(`/users/${id}/roles`)
    .map(response => response.json().map(x => UserRole[x]));
}

In case you get a Typescript error, you might need to cast the json result first, like so:

return this.http.get(`/users/${id}/roles`)
    .map(response => (<string[]>response.json()).map(x => UserRole[x]));
}

answered Dec 12, 2017 at 16:09

Kirk Larkin

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