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In the last lesson we looked at how we would update and delete documents in our MongoDB database.
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In this lesson I want to briefly look into how you might establish relationships between your documents
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and embed documents into each other through the use of Mongoose.
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We know that we currently have a single person in our people's collection who's called John and he has
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an age of 37.
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What if we could get John to have a favorite fruit which embeds a fruit document from our fruits collection?
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Well the way that we would do this is we would have to establish a relationship.
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Now we can't simply just call a person.updateOne and add in a brand new field that doesn't exist
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in the schema because you can't have a new field that's not specified in the schema.
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But what we can do though is we can add a new data entry, say for example if we were to create a new
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person who now has a favorite fruit, inside the person's schema we're going to update this.
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So we're going to change it so that we have a favorite fruit.
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And this is going to have a data type of fruitSchema.
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This tells Mongoose that we are embedding a fruit document inside this property called favoriteFruit
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in our person document.
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We can now create a new fruit and let's say it's a pineapple.
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This is going to be a new fruit which has a name of
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pineapple (piña) and it's got a score of 9 and a review of "Great fruit".
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So now that we created this new fruit called Pineapple, let's go ahead and save it. And let's call pineapple
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.save to save it into all fruits collection.
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And then we're going to add this pineapple as an embedded document in a new person. And this person
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is going to be called Amy and she's 12 and she has a favorite fruit. And that favorite fruit is of course
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the pineapple document that we created up here.
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Now let's uncomment person.not save to save Amy into our database of people and let's save and go over
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to a hyper terminal and run node app.js. And let's go over to our Mongo shell.
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So I want to show you firstly that if we go into db.people.find you can see that we have two
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records.
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One is John who's age 37 and he doesn't have a favorite fruit, but the other one is Amy and she's 12
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but she has a favorite fruit and this is an embedded document.
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So it's a fruit with a particular ID, a name of pineapple and a review.
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The ID of this fruit is something something something
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and it ends with a22.
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If at this point you go into your fruits database and you look at everything that's in there, you can
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see that the pineapple that's logged in here has exactly the same ID.
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We now have this pineapple objects in the fruit collection that is linked to have a relationship with
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a person in the people collection. So now as a challenge I want you to create a new fruit, to save that
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fruit to the fruits collection, and to assign that fruit as the favorite fruit for John because even
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though MongoDB allows us to have these asymmetrical data entries, for example this person doesn't
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have a favorite fruit
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but this one does because we updated the schema.
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But let's give John a favorite fruit as well.
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And in the process you'll get to create a new relationship.
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Pause the video and give that ago.
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Okay.
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So let's first create our new fruit.
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Let's say we're creating a Mango and it has a name of a Mango
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and it has a score of whatever it is you want it to be
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and it's also a pretty decent fruit.
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So now we're going to save this mango into our fruits collection and we're going to instead of create
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a new person, we're going to update our person namely John.
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So we're going to call upon the person model which will tap into our people collection and we're going
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to call the updateOne method. And we're going to pass in the condition that we want to find the document
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that we want to update.
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So in this case it's going to be a person with a name of John. And the update that we want to make is
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we want to change his favorite fruit to now have a value and it's going to be a mango. Not a mongo
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but a mango.
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And finally we're going to add the callback to check if there was an error.
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And it seems like despite my best efforts, I still spelt it as mongo.
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So let's change that and try again.
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Now it should have worked and it has successfully updated the document.
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So now if we go and check out our fruits we now have a new mango fruit in there.
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And if we check out our people, John now has a favorite fruit embedded into his record.
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So this is an overview of how you can use MongoDB with Node.js by leveraging the simplicity and the
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power of Mongoose.
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Now in the next module we're going to be taking this one step further
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and we're going to apply what we learned about Mongoose and MongoDB to our to do list to make it into
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a real working application that's able to persist the data that we save into the to do lists.
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So for all of that and more I'll see you on the next module.