1

I'm new to Rxjs (and Angular2 in general) and I'm having trouble understanding the subtleties of RxJS.

I want to make two REST calls to the GitLab API:

  1. Receive all the groups of a certain user (via gitlab.com/api/v4/groups). this will give me back a JSON like this one:

    [
{
    "id": 1511397,
    "name": "some name",
    "parent_id": 1505403,
...
},
{
    "id": 1511403,
    "name": "some other name",
    "parent_id": 1505403,
...
}
]

  2. Receive all the projects of per group (via gitlab.com/api/v4/groups/:id) which give you a detailed version of 1 group:

    {
"id": 1511397,
"name": "group name",
"parent_id": 1505403,
"projects": [
    {
        "id": 3099499,
        "description": "project 1"
    },
    {
        "id": 3099489,
        "description": "Project 2"
    }
]
}

So basically I need to loop over all ID's given by the first request and deliver an array of group-details:

[
 {
 "id": 1511397,
 "name": "group name",
 "parent_id": 1505403,
 "projects": [
     {
         "id": 3099499,
         "description": "project 1"
     },
     {
         "id": 3099489,
         "description": "Project 2"
     }
 ]
 },
 {
 "id": 1194997,
 "name": "a second group name",
 "parent_id": 152393,
 "projects": [
     {
         "id": 9423423,
         "description": "project 3"
     },
     {
         "id": 2394238,
         "description": "Project 4"
     }
 ]
 }
]

How can this be done? I already tried something along the lines of switchMap, concatMap and MergeMap, but I never can get it to work...

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2 Answers 2

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1

you can do something like this

getGroups() {
  return this.http.get('gitlab.com/api/v4/groups')
    .map(res => res.json()) // convert to object[]
    .map(res => res.map(g => g.id)) // get all id
    .mergeMap(gid => {
      let gs = [];
      gid.forEach(id => {
        let req = this.http.get(`gitlab.com/api/v4/groups/${id}`);
        gs.push(req);
      });
      return Observable.forkJoin(gs);
    })
    .map(res => { // we have array of Response Object
        return res.map(x => x.json()); // Array.map not Observable map operator.
    });
}

getGroups().subscribe(res => console.log(res))
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0

Something like that. You need to replace static Observable.of to $http observables.

Rx.Observable.of([{userId:1}, {userId:2}])
.switchMap(ids => Rx.Observable.of(...ids))
.mergeMap(userId => {
 return Rx.Observable.of([
   {userId:userId, name:'project1'},
   {userId:userId, name:'project2'}
 ]);
})
.subscribe(x=>console.log(x));
  1. Rx.Observable.of([{userId:1}, {userId:2}]) - is like http call that gives u array of users 2 .switchMap(ids => Rx.Observable.of(...ids)) - for each user you create a separate observable
  2. .mergeMap for each user observable you call $http to get projects.
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