Validate Request Payload with a Custom Pipe

Cross-field validation and custom pipe

NestJS offers a robust set of built-in pipes for general data validation tasks, ensuring the integrity of our data. However, in specific scenarios like cross-field validation, we might need a custom pipe to meet our unique requirements. Cross-field validation involves applying rules that consider multiple fields within a request payload.

In this lesson, we’ll delve into creating a custom pipe to handle a cross-field validation scenario.

Custom pipe

In NestJS, a custom pipe is implemented as a class that adheres to the PipeTransform interface. To create one, we must implement this interface, which requires defining a single method called transform(). This method takes two arguments, which are given below:

• value: This is the value to be transformed.

• metadata (optional): This is a parameter describing the value argument.

Below is a simplified example of how to create a custom pipe: