This piece of code defines a property in an entity...

This piece of code defines a property in an entity (likely using TypeScript and a library like TypeORM) that maps to a database column. Here's a breakdown of what the code does:

1. @Column decorator:
   This is a TypeORM decorator used to define a database column and its properties.

2. Column attributes:

   • name: 'delivery_radius_km': The name of the column in the database is explicitly set as 'delivery_radius_km'.
   • default: 5: Sets the default value for this column to 5 if no value is provided.
   • type: 'decimal': Maps this column's database type to DECIMAL in SQL, which supports numeric values with precision and scale.
   • precision: 5: Defines the total number of digits for the DECIMAL type (both before and after the decimal point). For example, 123.45 would have a precision of 5.
   • scale: 2: Defines the number of digits after the decimal point. In this case, the column can store values with up to two decimal places.
   • transformer:
     • to: Specifies how data is transformed before it is written to the database. In this example, it takes a number and directly stores it without any transformation.
     • from: Specifies how data is transformed when read from the database. In this example, it converts a string value from the database into a number using parseFloat.

3. deliveryRadiusKm:

   • This is the name of the property on the entity class in TypeScript. It is of type number and is mapped to the 'delivery_radius_km' column in the database.

Summary:

This code sets up a database entity field named deliveryRadiusKm (mapped to the delivery_radius_km column). It stores a decimal value with a precision of 5 and a scale of 2 (e.g., 123.45). The default value is 5, and the transformer ensures the data is properly handled when converting between the database and the application (numbers are stored as-is but converted to/from strings in the database).