Why is mongo telling me I need two arguments for $in in the query below?-CodePudding

I have the following query:

const productTypes = await ProductTypes.find(
        {type},
        {
            style: {
                $in: styles
            }
        }      
);

This is my styles array:

styles [ 'mom' ]

And I get this error:

MongoServerError: Expression $in takes exactly 2 arguments. 1 were passed in.

CodePudding user response：

At first glance, it looks like your query is wrong. You need so move the style query into the first param {type}.

You can check out a live query here

Something like this:

const productTypes = await ProductTypes.find({
  type,
  style: {
    $in: styles // ["mom"]
  }
});

This is the same stuff from the live demo... putting it here for archival purposes.

Test Database

[
  {
    "type": "a",
    "styles": [
      "mom",
      "dad",
      "sister"
    ]
  },
  {
    "type": "b",
    "styles": [
      "mom",
      "brother",
      "dad"
    ]
  }
]

Query

db.collection.find({
  type: "a",
  styles: {
    $in: [
      "mom"
    ]
  }
})

Result

[
  {
    "_id": ObjectId("5a934e000102030405000000"),
    "styles": [
      "mom",
      "dad",
      "sister"
    ],
    "type": "a"
  }
]