How can I create custom types in Flask ORM?

How can I create custom types in Flask ORM?

You can create custom types in Flask ORM by subclassing the TypeDecorator class from SQLAlchemy. This allows you to define how your custom type should be stored in the database and how it should be represented in Python.

Can you give me an example of a custom type?

Sure! For instance, if you want to create a custom type for a JSON field, you can do something like this:

from sqlalchemy.types import TypeDecorator, JSON

class JSONType(TypeDecorator):
    impl = JSON

    def process_bind_param(self, value, dialect):
        return value if value is not None else {}  # Default to empty JSON

    def process_result_value(self, value, dialect):
        return value if value is not None else {}  # Handle None values

How do I use this custom type in my model?

You can use the custom type in your model like this:

class MyModel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    data = db.Column(JSONType)

What if I want to add validation to my custom type?

You can add validation in the process_bind_param method. For example, you can check if the value is a valid JSON before storing it.