Update array element in mongo

Question

I want to update an array that I have in a mongo doc. The structure of which looks something like:

{
  _id: id,
  myArray: [
    {key1: val, key2: val, key3: va         


        

Answer 1

When mongodb queries an array field it provides a positional operator $ which you can use to access a specific element in that array. You can use an elemMatch operator to search into the fields within an array of objects.

Example:

db.myCollection.find({
   _id: ObjectId("53b1a44350f148976b0b6044"),
   myArray: {
      $elemMatch: {key1: 'somevalue'}
   }
}, {
   $set:{
      'myArray.$.key2': 'someOtherValue'
   }
});

See: http://docs.mongodb.org/manual/reference/operator/update/positional/