Many-to-many relation in loopback with different relation property name - loopback

Question

I've the following models:
Account
Page
AccountPage
the AccountPage is a "through" model, here are my configurations for those models
AccountPage.json
{
"name": "AccountPage",
"base": "PersistedModel",
"idInjection": true,
"options": {
"validateUpsert": true
},
"properties": {
"subscriptionDate": {
"type": "date"
}
},
"validations": [],
"relations": {
"subscriber": {
"type": "belongsTo",
"model": "Account",
"foreignKey": "subscriberId"
},
"page": {
"type": "belongsTo",
"model": "Page",
"foreignKey": "pageId"
}
},
"acls": [],
"methods": {}
}
Page.json
{
"name": "Page",
"base": "PersistedModel",
"idInjection": true,
"options": {
"validateUpsert": true
},
"properties": {
"title": {
"type": "string"
}
},
"validations": [],
"relations":
"subscribers": {
"type": "hasMany",
"model": "Account",
"foreignKey": "subscriberId",
"through": "AccountPage",
"keyThrough": "pageId"
}
},
"acls": [],
"methods": {}
}
Account.json
{
"name": "Account",
"base": "User",
"idInjection": true,
"options": {
"validateUpsert": true
},
"properties": {},
"validations": [],
"relations": {
"pages": {
"type": "hasMany",
"model": "Page",
"foreignKey": "",
"through": "AccountPage",
"keyThrough": "subscriberId"
}
},
"acls": [],
"methods": {}
}
When I access GET /Pages/{id}/subscribers, I got
"Relation \"account\" is not defined for AccountPage model"
If I change "subscriber" relation name in AccountPage.json to "account" it works ok, is this a bug or am I do something wrong?

Answer 1

I figured it out, it was misconfiguring the foreignKey and keyThrough in Page, and Account models. The foreignKey of Account relation in the Page model should have foreigKey of pageId, as according to the documentation "Specify custom foreignKey (for this model) on the related model" so it should be pageId not subscriberId.
So Page model relation will be (Page.json):
"subscribers": {
"type": "hasMany",
"model": "Account",
"foreignKey": "pageId",
"through": "AccountPage",
"keyThrough": "subscriberId"
}
and Account model relation will be (Account.json):
"pages": {
"type": "hasMany",
"model": "Page",
"foreignKey": "subscriberId",
"through": "AccountPage",
"keyThrough": "pageId"
}
Now it is working fine