Tai Chi (太極)

Emphasis on both hard and soft

A new way to deal with your Data Logic of SQL Databse. You can define a virtual field called ComputeProperty (that actually is SQL statement) for a data model.

Introduction

• The common data logics in form of ComputeProperty of Data Model become more reusable.
• The codes of data query become more human readable because complex data logics can be abstracted in ComputeProperty.
• Flexible and strong Model API. Without using QueryBuilder, Model.find() is powerful enough to build complex logics by extending or modifying the ComputeProperty.
• Developed in Typescript but you can use it without typescript compiler.
• Common relation logics such as HasMany and belongsTo are can be defined in form of ComputeProperty. And the related Models are queried in one single Sql call.

View Full Document Here

Basic usage of ComputeProperty

Imagine an E-commerce system. A product (Model) has various fields like availableStart, availableEnd and remainingStock. A product is active when the current time are within these dates and the remainingStock are not zero. We can define the schema like below (with a isActive ComputeProperty). ComputeProperty consist of ComputeFunction that defines how to make a SQL value (we called Scalar). The variable parent represents the Datasource of Product Model. The property isActive combines the values of other FieldProperty.

export default class Product extends Model {

    //define field properties here
    id = this.field(PrimaryKeyType)
    availableStart = this.field(DateNotNullType)
    availableEnd = this.field(DateNotNullType)
    remainingStock = this.field(NumberNotNullType)

    //define ComputeProperty based on the value of FieldProperty
    isActive = Product.compute((parent) => {
        return new Scalar<BooleanNotNullType, any>(context => context.$.And(
            parent.$.availableStart.lessThan( new Date() ),
            parent.$.availableEnd.greaterThan( new Date() ),
            parent.$.remainingStock.greaterThan(0)
        ))
    })
}

Below the ModelRepository.find() function accepts one argument FindOptions (Just like the other ORM). The where part specifies the data filtering condition. You can use the isActive ComputeProperty simply just like a normal field (FieldProperty) in the where object.

let activeProducts = await Product.find({
  where: {
    isActive: true
  }
})

Acknowledgement

Thanks Knex. The project is heavily using Knex.

Development?

If you are interested and agreed with the ideas, you may join our project. You can talk in the discussion board.

git clone ...

# Start the project. It is built by typescript
npm run dev

# Start one more terminal. It starts a database server
docker-compose up

# Start another terminal. Run the unit tests
npm run test