medusa-store/docs/content/advanced/backend/price-selection-strategy/override.md

Override Price Selection Strategy

In this document, you’ll learn how to override Medusa’s price selection strategy to create a custom pricing strategy.

:::note

If you’re interested in learning what a price selection strategy is and how it works, check out this documentation instead.

:::

1. Create Class

Create a TypeScript or JavaScript file in src/strategies of your Medusa server project with a class that extends the AbstractPriceSelectionStrategy class:

import { AbstractPriceSelectionStrategy, IPriceSelectionStrategy, PriceSelectionContext, PriceSelectionResult } from "@medusajs/medusa";

import { EntityManager } from "typeorm";

export default class MyPriceListStrategy extends AbstractPriceSelectionStrategy {

  withTransaction(manager: EntityManager): IPriceSelectionStrategy {
    if (!manager) {
      return this
    }

    return new MyPriceListStrategy()
  }

  async calculateVariantPrice(
    variant_id: string,
    context: PriceSelectionContext
  ): Promise<PriceSelectionResult> {
    //TODO
  }
}

You can use services or repositories in the strategy by adding them to the constructor and updating the parameters passed to the MyPriceListStrategy constructor in withTransaction. For example:

export default class MyPriceListStrategy extends AbstractPriceSelectionStrategy {
  private productsService: ProductService

  constructor({
    productsService
  }) {
    super()
    this.productsService = productsService
  }

  withTransaction(manager: EntityManager): IPriceSelectionStrategy {
    if (!manager) {
      return this
    }

    return new MyPriceListStrategy({
      productsService: this.productsService
    })
  }
  //...
}

---

2. Implement calculateVariantPrice

Implement the price selection strategy you want inside the calculateVariantPrice method.

This method accepts the variant ID as a first parameter and the context object as a second parameter.

This method must return an object having the following fields:

{
  originalPrice, //number | null
  calculatedPrice, //number | null
  prices // MoneyAmount[]
}

You can learn more about optional properties and the meaning behind every property here.

---

3. Run Build Command

In your terminal, run the build command to transpile the files in the src directory into the dist directory:

npm run build

---

Test it Out

Run your server to test it out:

npm run start

Then, try out your strategy using any of the Products or Carts endpoints which include retrieving product variants and line items respectively. You should then see the prices in the response based on your implemented strategy.

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What’s Next 🚀

• Learn more about price list selection strategy.