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LB4 vs. LB3

How LoopBack 4 creates/handles models. [2019 July 24]

In lb4, we introduce the concept of repository. In order to implement this new feature repository, we are using juggler bridge. Each model has two parallel classes:

• The class defined by the app developers using decorators and class MyModel extends Entity syntax.
• The "implementation" class created by legacy-juggler-bridge, this class is inheriting from juggler's Model base class.

If you take a deep look into it, you would find that LB4 model handles some data before it hands the model to Juggler. That's why lb4 has some differences compared to lb3 when generating models.

For example, you might notice that some entries in @model decorator are not available/supported by lb4 even they both run the same lines of code in Juggler. For instance, the default values for the strict entry in @model decorator are different:

	in LB3	in LB4
default	false	true
code	defined here	defined here

Hope this example shows the idea that even they both use the base model from Juggler, LB4 model doesn't use, or even have access to some fields/entries in the Juggler model!

Happy coding :D