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Now that you’ve tested the persistence of data, you’ll need methods to access that data.

Mongoose schemas support

static methods: methods called by a model. They typically operate on a collection of documents (instances of the model).
instance methods: methods called by an instance of a model. They typically operate on the document (model instance) itself.

From the previous exercise, you might recognize Dinosaur.findOne() as a static method and dino.save() as an instance method.

Sometimes you need to define additional methods for your application, like if you see a server-level error such as this:

TypeError: Dinosaur.findByName is not a function

This server test is failing because there is no model method to find Dinosaurs by name. You’ll need to drop to the model layer and write more tests.

The desired query is performed on a collection of documents, so it requires a static method, which is defined in [schema].statics and called according to the example below.

// static method - implementation
DinosaurSchema.statics.findByName = function(name, callback) {
  return this.findOne({ name: name }, callback);
};
// static method - call the method
await Dinosaur.findByName('Velociraptor')

Use function() notation instead of arrow => notation to properly bind this.

You can test-drive the development of this method just like any other JavaScript method: Call the method and make assertions on its output.

Instructions

Test-drive the static method findByName(name), which returns the first document that matches a given name.

In dinosaur-test.js under it('returns the first match on name' (scroll to the bottom of the file) add the following setup:

      const fields = {
        name: 'Pterodactyl',
        count: 5,
        risk: 'Low'
      };
      const dino = new Dinosaur(fields);
      await dino.save();

Call await Dinosaur.findByName('Pterodactyl') and store the result in a variable named stored.

Using assert.include, assert that stored contains the same key-values pairs as fields.

Run npm test and see the error message

TypeError: Dinosaur.findByName is not a function

In dinosaur.js, define an empty findByName method in DinosaurSchema.statics.

Use function() {} notation.

Run npm test and see the error message

AssertionError: Target cannot be null or undefined.

In dinosaur.js, add the implementation code provided in the narrative above.

Make sure to add name and callback parameters to the function.

Run npm test and see green!

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