VirtualType

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VirtualType()

Parameters:
  • options «object»
    • [options.ref] «string|Function» if ref is not nullish, this becomes a populated virtual
    • [options.localField] «string|Function» the local field to populate on if this is a populated virtual.
    • [options.foreignField] «string|Function» the foreign field to populate on if this is a populated virtual.
    • [options.justOne=false] «boolean» by default, a populated virtual is an array. If you set justOne, the populated virtual will be a single doc or null.
    • [options.getters=false] «boolean» if you set this to true, Mongoose will call any custom getters you defined on this virtual
    • [options.count=false] «boolean» if you set this to true, populate() will set this virtual to the number of populated documents, as opposed to the documents themselves, using Query#countDocuments()
    • [options.match=null] «object|Function» add an extra match condition to populate()
    • [options.limit=null] «number» add a default limit to the populate() query
    • [options.skip=null] «number» add a default skip to the populate() query
    • [options.perDocumentLimit=null] «number» For legacy reasons, limit with populate() may give incorrect results because it only executes a single query for every document being populated. If you set perDocumentLimit, Mongoose will ensure correct limit per document by executing a separate query for each document to populate(). For example, .find().populate({ path: 'test', perDocumentLimit: 2 }) will execute 2 additional queries if .find() returns 2 documents.
    • [options.options=null] «object» Additional options like limit and lean.
  • name «string»

VirtualType constructor

This is what mongoose uses to define virtual attributes via Schema.prototype.virtual.

Example: 

const fullname = schema.virtual('fullname');
fullname instanceof mongoose.VirtualType // true

VirtualType.prototype.applyGetters()

Parameters:
  • value «any»
  • doc «Document» The document this virtual is attached to
Returns:
  • «any» the value after applying all getters

Applies getters to value.

VirtualType.prototype.applySetters()

Parameters:
  • value «object»
  • doc «Document»
Returns:
  • «any» the value after applying all setters

Applies setters to value.

VirtualType.prototype.get()

Parameters:
  • fn «Function»
Returns:
  • «VirtualType» this

Adds a custom getter to this virtual.

Mongoose calls the getter function with the below 3 parameters.

  • value: the value returned by the previous getter. If there is only one getter, value will be undefined.
  • virtual: the virtual object you called .get() on.
  • doc: the document this virtual is attached to. Equivalent to this.

Example: 

const virtual = schema.virtual('fullname');
virtual.get(function(value, virtual, doc) {
  return this.name.first + ' ' + this.name.last;
});

VirtualType.prototype.set()

Parameters:
  • fn «Function»
Returns:
  • «VirtualType» this

Adds a custom setter to this virtual.

Mongoose calls the setter function with the below 3 parameters.

  • value: the value being set.
  • virtual: the virtual object you're calling .set() on.
  • doc: the document this virtual is attached to. Equivalent to this.

Example: 

const virtual = schema.virtual('fullname');
virtual.set(function(value, virtual, doc) {
  const parts = value.split(' ');
  this.name.first = parts[0];
  this.name.last = parts[1];
});

const Model = mongoose.model('Test', schema);
const doc = new Model();
// Calls the setter with `value = 'Jean-Luc Picard'`
doc.fullname = 'Jean-Luc Picard';
doc.name.first; // 'Jean-Luc'
doc.name.last; // 'Picard'
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