Loopback API include filters not working as expected

问题

I have used different models to simplify what I am trying to achieve and to remove clutter, although the theory should be the same as my actual project.

Use the following assumptions: A system can only have one type of speaker and one type of amp.

Say I have the following models:

*** System ***
- id
- name
- speakerId
- ampId

*** Speaker ***
- id
- name

*** Amp ***
- id
- name

I have added the following to my System.json model file (which i think is correct):

"relations": {
    "speakers": {
      "type": "hasOne",
      "model": "Speaker",
      "foreignKey": "speakerId"
    },
    "amps": {
      "type": "hasOne",
      "model": "Amp",
      "foreignKey": "ampId"
    }
  },

When I start my app and open the API Explorer and go to create a new instance of Speaker or Amp it expects the following:

  *** Speaker ***
- id
- name
- speakerId   *** Why is this here??? ***

If I change the System.json model file to look like this (which I think is the wrong way to do it):

"relations": {
    "speakers": {
      "type": "hasOne",
      "model": "Speaker",
      "foreignKey": "id"
    },
    "amps": {
      "type": "hasOne",
      "model": "Amp",
      "foreignKey": "id"
    }
  },

Everything looks right in the API explorer. So I add a few speakers and amps, then add a system.

When I add an include filter to the System GET request:

{"include":["speakers","amps"]}

It includes the speakers and amps but using the System.id as the index for the Speakers and Amps Models instead of System.speakerId and System.ampId. So to ellaborate if the:

System.id = 5 
System.speakerId = 1
System.ampId = 3

It will include the speaker with an id of 5 and the amp with the id of 5 instead of including the speaker with an id of 1 and the Amp with an id of 3.

I want to be able to list all Systems including their related Speakers and Amps. How can this be done with Loopback. At the minute I am using the above models with in memory DB instead of my usual ones just to test. Any help would be appreciated as I am now at the point of tearing my hair out!

Regards, James

回答1:

Your relation between models is not correct. You need to tell loopbackjs to use hasMany through relation to get your data.

Your system.json should be changed to

"relations": {
"speaker": {
  "type": "belongsTo",
  "model": "Speaker",
  "foreignKey": "speakerId"
},
"amp": {
  "type": "belongsTo",
  "model": "Amp",
  "foreignKey": "ampId"
}},

And your speakers should be

"relations": {
    "amps": {
      "type": "hasMany",
      "model": "Amp",
      "foreignKey": "speakerId",
      "through": "System"
    },

amp.json

"relations": {
    "speakers": {
      "type": "hasMany",
      "model": "Speaker",
      "foreignKey": "ampId",
      "through": "System"
    },

来源：https://stackoverflow.com/questions/32252867/loopback-api-include-filters-not-working-as-expected

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