try_mongo/video_transcripts/5-building-with-mongoengine/5-mongoengine-entities_tran...

00:03 So far we've modeled our data with Python classes,
00:05 but there was no real MongoEngine entity stuff,
00:08 they wouldn't actually be saved or processed by MongoEngine.
00:11 It just happens to be we kind of sketched
00:13 them out in Python class style.
00:15 So we're going to change that now.
00:16 We're going to go make our standard, plain old Python classes.
00:19 Proper MongoEngine entities.
00:21 The snake is pretty simple.
00:22 So let's start there.
00:23 So in order to work with MongoEngine over here,
00:26 I'm going to have to import it.
00:28 Now, you might want to do
00:30 from MongoEngine, import some things,
00:32 but I like to be real explicit.
00:34 These things are coming from MongoEngine,
00:36 even in my production code.
00:37 So this is how I'm going to do it.
00:38 We're going to set the register date
00:40 to a particular type of descriptor
00:42 that comes from MongoEngine,
00:44 and at sort of the type of level this tells MongoEngine
00:47 what type of data, and constraints,
00:49 and requirements go onto this field.
00:52 However, at run time, it's going to act like,
00:54 say date time or whatever it is.
00:56 In this case the date time
00:57 and species would be string and so on.
00:58 So we'll come over and say "mongoengine.DateTimeField()"
01:02 and we'll just go like this.
01:03 This will tell MongoEngine to map
01:04 that to the database as a date-time field.
01:06 Over here, we'll say "mongoengine.StringField"
01:09 and over here, the length,
01:11 let's say this is in meters and that's probably decent floats.
01:15 alright so this will be a float field.
01:17 The name, again is string field.
01:19 Whether it's venomous or not, that's true or false.
01:22 It could be a number, like level of venomous.
01:24 I don't know, but we're going to call this a boolean field
01:27 and that's that.
01:27 So our snake is all ready to map into MongoDB.
01:31 MongoDB doesn't have things like required fields
01:34 or default values or anything like that,
01:36 but MongoEngine does.
01:37 So let's change this to make it a little simpler
01:39 to create a snake.
01:40 So for example, "registered_date" is almost always just
01:43 whenever you inserted it, right?
01:45 So what we can do is we can come over here
01:46 and set a default function
01:47 that will execute any time MongoEngine inserts a new snake.
01:50 So we're going to start with date-time.
01:52 So the function that we want to call is the now function
01:55 which gives us the full year, month, day,
01:58 hour, minute, second representation of time.
02:00 So we'll come in here, say "datetime.datetime.now"
02:03 and be very careful not to put the parenthesis.
02:06 You're passing the function, not the value of "now"
02:08 That would be when the program started.
02:10 So that can be a little tricky.
02:11 Over here for species, let's say that you have
02:13 to say the species.
02:14 So we're going to say this is going to be required is true.
02:17 In fact, the length is required, the name is required,
02:20 whether it's venomous is required.
02:22 We can have things like minimum values have to be like 0.001
02:27 or things like this.
02:29 So you can't have like a negative length.
02:30 There's a lot of cool constraints
02:32 that we can do with our types here.
02:33 So this snake is now ready to be used in our database.
02:38 Let's look at the next one.
02:39 Let's work on the cage next.
02:41 So again, import MongoEngine and we'll use that
02:43 in a few places.
02:44 This is exactly the same here.
02:46 So set the default and then the name is
02:48 just going to be string and so on.
02:50 So I'll just sketch these out for you.
02:53 So these seem like reasonable types here, and let's go ahead
02:55 and set the required properties for things that we require.
02:59 Most of these would be required,
03:01 and whether or not we allow dangerous snakes.
03:03 If you don't set that, let's say no,
03:05 by default you're not going to have a dangerous snake.
03:08 Okay, so these are just like the snake before.
03:10 This however, gets more interesting.
03:12 We're going to come down here and we're going to set this
03:14 to be a "mongoengine.EmbeddedDocument"
03:18 We can have just a single thing, like a booking
03:20 or embed the snake in the owner or something like that,
03:25 but we want to have a list of embedded documents
03:28 and what we need to pass in here is the actual type
03:32 that is contained in there.
03:32 So we're going to import "data.bookings.Booking"
03:35 One other thing that I also realized that I forgot to do
03:38 in the previous ones and we'll go back and fix that,
03:39 is we need to tell MongoEngine
03:41 that this is a top level document.
03:43 We need to make this have a base class of type document.
03:47 We'll do that for snakes as well.
03:54 Now let's go to the booking, we were just working with that.
03:56 So this one, recall, is the type
04:00 that's embedded within the cage
04:03 That's embedded in the cage, that means it's not a document.
04:06 Right? That would be a top level thing.
04:07 This is an embedded document.
04:09 Alright, so this can be contained within other documents,
04:11 but itself cannot be top level.
04:14 Let's go ahead and set these, as well.
04:18 Now, when we're talking about IDs in MongoDB,
04:20 the default is something called an object ID.
04:23 Like a UID, or GUID or something,
04:25 so when we're talking about a reference,
04:27 typically it doesn't have to be, but it typically is.
04:33 There we go.
04:34 We've got our two references as object IDs.
04:37 We've got our booking date,
04:38 which does not have to be required,
04:39 and it doesn't have a default value.
04:41 This is when was booked,
04:42 which happens after the booking slot was made available,
04:47 but at the time of creation of the slot of booking, right,
04:50 we've like put a note for booking.
04:51 You have to say the check in and check out date,
04:53 and again, the reviews.
04:55 These are not getting set until after.
04:58 I set this to zero so we can say,
05:00 like, you know, required to be one to five.
05:03 They actually rate the thing and then you
05:05 can sort of exclude the ones that are zero.
05:08 The final one is owner and it's very, very similar.
05:10 I'll just sketch that out for you.
05:13 We've got our flat pieces here.
05:15 Our register date, name and email
05:17 and now we're going to have a list of IDs.
05:19 So we'll come in here and say "mongoengine.ListField"
05:23 for both of them.
05:26 So this'll let us store the object IDs
05:28 that refer to the snakes and the object IDs
05:30 that refer to the cages.
05:32 Last thing to do is make the base class the document here.
05:36 Alright, so what have we done?
05:38 We've set all of the fields to their respective types
05:41 out of MongoEngine as descriptors.
05:43 We've set either default or required values
05:46 and we've set the metadata,
05:48 which talks about which database connection to use
05:50 and what to call the collection
05:52 when it goes into the database.
05:54 And we've done that for our three top level items here.
05:58 The one that is different and stands out is the booking,
06:00 which is embedded within the cage
06:03 and this is an embedded document,
06:06 but otherwise everything goes pretty much the same.