tworkman512/w3-mongo

MongoDB

By the end of this lesson, you should be able to connect to a non-relational database (MongoDB) and perform basic CRUD operations.

Core Learning Objective

• Interact with a document database

Sub-Objectives

• Connect to a MongoDB database with Mongoose
• Perform basic CRUD operations on the database
• Build and run specific queries
• Validate schemas
• Model complex application ideas using embedded data models

Installation

1. Fork & clone

2. cp nodemon.sample.json nodemon.json

3. Create a new Cluster on MongoDB Atlas titled something like general-purpose or reuse one you already have.

4. Update the MONGO_DB_CONNECTION in your nodemon.json file with the full connection string. Make sure you include the password you set up for the database and change the name of the database from test to something lke television_characters_dev.

5. npm install

6. npm run dev

Once installation is working, try creating and requesting resources. Note that there is currently no validation set up.

Instructions & Guiding Questions

• Take a moment to look through the code that already exists in this repository. Run the code and test out each route, ensuring it does what you expect.

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• We will be using both mongoose and mongodb to build this project. Open up each project's documentation.

• Question: What is the difference between mongoose and mongodb?

• Your Answer: MongoDB is a NoSQL document database that allows us to store data. Mongoose is a Object-Document Mapper or (ODM), see https://www.mongodb.com/blog/post/part-2-introducing-mongoose-to-your-nodejs-and-restify-api, library for working with, or speaking to, a MongoDB. More specfically, Mongoose help us define how objects in the database should look like and also help with creating Modeal and Schemas to manage the content within our database.

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• MongoDB uses a number of terms that may be to new to you such as database, collection, and document.

• Question: What is the difference between the above terms? This page may help.

• Your Answer:

• Document is a record or representation of data in MongoDB.
• Collections are a group of MongoDB documents or records.
• Database is a physical container for collections.

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• Create a new file with the path of api/models/series.js. In that file, define the schema for a television series. Include the fields "title", "start_year", and "season_count".

• Question: Where does String and Number come from?

• Your Answer: They just come from JavaScript. Specifically, the global constructor.

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• Merge the following into your schema:

  {
    _id: Schema.Types.ObjectId;
  }

• Question: Describe what the above code is adding to your schema.

• Your Answer: It represents a unique key identifier or serielization on the specified Object that is a long string. This is specific format that Mongoose uses internally. We'd typically use this when defining a Schema object.

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• Remove the line we just added from your schema.

• Question: If we create a new document, will there be an ID? Why or why not?

• Your Answer: Yes. Mongoose creates a unique key for us by default that is stored under _id.

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• Add the following object as the second argument to the new Schema() statement.

  {
    timestamps: { createdAt: 'created_at', updatedAt: 'updated_at' }
  }

• Question: Describe what the above code is adding to your schema.

• Your Answer: It allows us to store the time a record was created and updated. The key/value pairs are re-mapping the keys to some other values.

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• Import the model into your routes/series.js file. Use either basic promises or async/await to update the GET / method to retrieve from the database instead of the given array. This page or this page may be useful.

• Question: What method do you use to return all documents from a collection? `
• Your Answer: Using the Model.find(), for this app it would be Series.find(), method will return us all the documents from a collection.

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• Update the API so that you can create documents in the database. You may either use the <document>.save() method or the Model.create() method.

• Question: What happens if you do not include all the fields as specified in the schema?

• Your Answer: It only records the fields that are included in the POST.

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• Take a moment to view your new document in the MongoDB Atlas console.

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• Update the API so that you retrieve a document by ID.

• Question: There are a couple different ways to accomplish this goal. Which method did you choose?

• Your Answer: I chose the Model.findById() method.

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• Update the API so that you are able to update a document. Use the Model.updateOne() method.

• Question: What are the arguments for Model.updateOne()?

• Your Answer: They are filter, doc. filter is looking for a match on the object that is passed in and doc will update whichever key/value pair is passed in as the second argument once the filter match has been found. There are also options and callback available.

• Question: The response you receive is not the document you updated. What information is being represented here? Try replacing Model.updateOne() with the Model.findOneAndUpdate() and see the difference in the result.

• Your Answer: It seems like Model.updateOne() will return back meta data about the request. Model.findOneAndUpdate() will return back the old version of the document that was updated.

• Question: This new method will return the old document instead of the new one. What option can you add to your statement to return the new one?

• Your Answer: We can pass in the new option, which if true, will return the modified document.

• Question: Another field was updated when you ran this command. Which one was it?

• Your Answer: updated_at was updated with a new time stamp.

• Question: Take a look at the terminal window running your server. You are likely getting the following deprecation warning:

  DeprecationWarning: Mongoose: `findOneAndUpdate()` and `findOneAndDelete()` without the `useFindAndModify` option set to false are deprecated. See: https://mongoosejs.com/docs/deprecations.html#-findandmodify-
  

  Take a look at this page to see how to fix it. Describe the changes that took place.

• Your Answer: Adding useFindAndModify: false to mongoose.connect() in our app.js file makes the error in the terminal disappear.

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• Update the API so that you can successfully delete a record. Use the Model.findOneAndDelete() method.

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• A lot of information is being returned on each request. Some of this information we may want to keep private. Using the .select() method, return only the "_id", "title", "start_year", and "season_count" on all the above requests.

• Question: At least one of these will throw an error. Which one? How can you get around this issue?

• Your Answer: POST threw a 400 error because the server could not process the request being sent by the client. I've tried a number of the different query methods in the Mongoose docs to see if I could get around this and wasn't able to. Hoping we can cover the solution with more detail in class.

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• Modify your GET /api/series route so that you can search through the content based off of query parameters. For example, if your request was GET /api/series?start_year=1997, it would return all series that start in 1997.

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• At the moment, there is no validation set on creating any series. Add validation so that each of the three fields are required in order to post to series. Handle any errors that arise with a status code 400 and a brief, standardized message.

• Question: You may notice that you can add custom error messages to individual fields failing. Try adding these and take a look at the error message received. How can you make use of those specific messages for each field?

• Your Answer: With async/await we can add a try/catch block and then console.log() any errors we might get back. We can then use the console to help debug.

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• With Mongo, it is simple to create complex data structures. Add a characters field to your Series model that is an array of objects. Each object should have a name and image_url. Only the name field on the character should be required. Note: Don't forget to change your select statements to include the characters field!

• Question: Take a look at the response from making a new series with a character. What field was created that you did not have to define?

• Your Answer: Mongoose created a unique key identifies in the characters array.

• Question: With the current routes that we have, how would you upate the name of a character in a series?

• Your Answer: I would need to update the PUT route and attempted something like the following:

router.put("/:id/:id", async (req, res, next) => {
  const status = 200;
  const response = await Series.findOneAndUpdate(
    { _id: req.params.id },
    { title: req.body.title },
    { start_year: req.body.start_year },
    { season_count: req.body.season_count },
    { characters: req.body.characters.name },
    { new: true }
  );

  res.json({ status, response });
});

I was trying to see if I could drill down in the id's to get to the character name, but that doesn't work here. Hoping we can cover the solution with more detail in class.

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• While we can now update subdocuments, it is difficult to make changes that only relate to a single subdocument. To do so, we should make a new set of routes that relates to characters. Start by creating a GET ALL route for characters. The route will look something like the following and will return only the list of characters:

  GET /api/series/:seriesID/characters
  

• Question: Where did you decide to put this route and why?

• Your Answer: I followed the example code provided to us and placed the route in app.js. This made sense to me, since we would setup any additional routes for this app there. I also followed the provided example and broke out the GET request for characters in a separate file. After reviewing this file, I really liked the idea of breaking out request for subdocuments in a separate routes file to help keep our code clean and organized.

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Spend the rest of class building out the other routes for characters. A few notes to help:

• It's worth reading the subdocument documentation in full
• Take note of the .id() method for finding subdocuments by id
• Note that in order to save subdocuments, you will need to save the parent record; in our case, you should be calling series. save(), not character.save()

If you're interested in going further, I would recommend looking into references.

Resources

• MongoDB Atlas
• Mongoose