README
UCAST Objection
This package is a part of ucast ecosystem. It provides an interpreter that can interpret ucast conditions into Objection query.
Installation
npm i @ucast/objection
# or
yarn add @ucast/objection
# or
pnpm add @ucast/objection
Getting Started
Interpret conditions AST
First of all, you need AST to interpret it. For the sake of an example, we will create it manually:
import { CompoundCondition, FieldCondition } from '@ucast/core';
import { interpret } from '@ucast/objection';
import { Model } from 'objection';
class User extends Model {
static tableName = 'users'
}
// x > 5 && y < 10
const condition = new CompoundCondition('and', [
new FieldCondition('gt', 'x', 5),
new FieldCondition('lt', 'y', 10),
]);
interpret(condition, User.query()); // the same as User.query().where('x', '>', 5).where('y', '<', 10)
Conditions on related table
Interpreter automatically joins related table and adds condition on its column, when the corresponding field in AST contains . (dot). For example:
const condition = new FieldCondition('eq', 'address.street', 'some street');
interpret(condition, User.query()); // the same as User.query().joinRelation('address').where('address.street', '=', 'some street')
Custom interpreter
Sometimes you may want to add custom operator or restrict supported operators. To do this, you can create interpreter manually:
import { createObjectionInterpreter, eq, lt, gt } from '@ucast/objection';
const interpret = createObjectionInterpreter({ eq, lt, gt });
const condition = new FieldCondition('eq', 'x', true);
interpret(condition, User.query()); // the same as User.query().where('x', '=', true)
To add a custom operator, all you need to do is to create a function that applies Condition to passed in ObjectionQueryBuilder. Let's create an operator, that adds condition on publishedAt field of an Article:
import { DocumentCondition } from '@ucast/core';
import { ObjectionOperator, createObjectionInterpreter, allInterpreters } from '@ucast/objection';
const isActive: ObjectionOperator<DocumentCondition<boolean>> = (node, query) => {
const operator = node.value ? '>=' : '<';
return query.where('publishedAt', operator, new Date());
};
const interpret = createObjectionInterpreter({ ...allInterpreters, isActive });
const condition = new DocumentCondition('isActive', true);
interpret(condition, Article.query()); // Article.query().where('publishedAt', '>=', new Date())
Want to help?
Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on guidelines for contributing