How to remove a property before save - angularjs

Question

I'm using Angular to build my frontend and loopback at the backend, My Model has a relation HasManyThrough
// person.json
{
"name": "Person",
...,
"relations": {
"contacts": {
"type": "hasMany",
"model": "Person",
"foreignKey": "fromId",
"through": "PersonConnect"
}
}
}
// person-connect.json
{
"name": "PersonConnect",
"base": "PersistedModel",
"properties": ...,
"relations": {
"from": {
"type": "belongsTo",
"model": "Person",
"foreignKey": "fromId"
},
"to": {
"type": "belongsTo",
"model": "Person",
"foreignKey": "toId"
}
}
}
If I try with the explorer I can build a new relation between two people using
PUT /api/Person/:id/contacts/:fk
Where id, the fromId and fk is the toId, the problem is Angular SDK generate services is sending also the body parameters id and fk, this make problems because the set the PersonConnect.id equal to Person.fromId and also appends a extra value fk
{
"_id" : ObjectId("55f0915f19c46e06675d056e"),
...
"fromId" : ObjectId("55f0915f19c46e06675d056e"),
"toId" : ObjectId("55f09b4d4d06f8c872e43c84"),
"fk" : "55f09b4d4d06f8c872e43c84"
}
To fixed I write the following
// person-connect.js
var _ = require('lodash');
module.exports = function (PersonConnect) {
PersonConnect.observe('before save', function (ctx, next) {
if (ctx.instance) {
ctx.instance = _.omit(ctx.instance, ['id', 'fk']);
}
next();
});
};
Without success, the id, and fk values still are using the send values, I set to null and works but I get something like
{
"_id" : ObjectId("55f18c67bbfa11053b36cafc"),
...
"fromId" : ObjectId("55f0915f19c46e06675d056e"),
"toId" : ObjectId("55f09b4d4d06f8c872e43c84"),
"fk" : null
}
How I can delete properties before store a model in loopback?

Answer 1

You can try using unsetAttribute instead:
ctx.instance.unsetAttribute('unwantedField');