get（）将数组作为非数组返回

Question

I have this model:

let model = new falcor.Model({
    cache: {
        hStudents: {
            801: {
                FirstName: 'Samuel',
                LastName: 'Forbes'
                },
            802: {
                FirstName: 'Chad',
                LastName: 'Pennington'
                }
            },
        lStudents: [
            $ref(['hStudents', 801]),
            $ref(['hStudents', 802])
            ]
        }
    });

When I execute the following code, although lStudents is an array in the model, I'm getting back an object which is not an array. For that reason, I cannot use Angular's *ngFor to iterate over the object. Why would I not get an array back?

return this.model.get("lStudents[0..1]['FirstName','LastName']")
    .progressively()
    .subscribe( (h) => {
        console.log(JSON.stringify(h));
        });

prints:

{"json":{
  "lStudents":{
    "0":{"$__path":["hStudents","801"],"FirstName":"Samuel","LastName":"Forbes"},
    "1":{"$__path":["hStudents","802"],"FirstName":"Chad","LastName":"Pennington"},"$__path":["lStudents"]}
  }
}

Answer 1

Falcor treats arrays as objects with keys equal to the array item's index. See the documentation example here .

The reason for this is that because the lStudents list is paginated, it will have to handle queries like "lStudents[10..19]['FirstName','LastName']" . If the result were to be an array rather than object, eg { "json": "lStudents": [ <items 10 - 19> ] } , it would conflict with a similar query asking for students 0 - 9 (or any other student list query).

To handle objects representing lists, convert the jsonGraph response to an array. A utility library like lodash or ramda might come in handy.

this.model.get("lStudents[0..1]['FirstName','LastName']")
    .progressively()
    .subscribe((jsonEnvelope) => {
       /* using Ramda and transforming 
        * { "FirstName":"Samuel","LastName":"Forbes" }
        * to { "FirstName":"Samuel","LastName":"Forbes", "index": "0" }
        */
        console.log(
          R.compose(
            R.map(([studentIdx, student]) => ({
              ...student,
              index: studentIdx
            })),
            R.toPairs
          )(jsonEnvelope.json.lStudents);
        );
        /* using Ramda and ignoring index
         */
        console.log(
          R.values(jsonEnvelope.json.lStudents)
        );
 });