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🛑 Pipes (Validation)

In NestJS, a Pipe is a class annotated with @Injectable() that implements the PipeTransform interface, typically used to validate or transform input data before it reaches the Controller.

In Ferrox, Pipes are implemented automatically through the Validation Extractor pattern, leveraging the validator crate.

High-Level Example​

To validate incoming JSON data, you simply need to decorate your Data Transfer Object (DTO) with validation rules, and use the Json extractor in your controller.

use axum::{Json, routing::post, Router};
use validator::Validate;
use serde::{Deserialize, Serialize};

#[derive(Debug, Serialize, Deserialize, Validate)]
pub struct CreateUserDto {
    #[validate(email)]
    pub email: String,
    
    #[validate(length(min = 8, message = "Password too short"))]
    pub password: String,
}

// The framework automatically runs the Pipe (validation) before executing this function
async fn register_user(Json(payload): Json<CreateUserDto>) -> Json<&'static str> {
    payload.validate().unwrap(); // Trigger the Pipe
    
    Json("User Created!")
}

Low-Level Internal Details​

While you can manually call .validate() inside the controller, Ferrox allows you to build custom Extractors that act as automatic Pipes.

By implementing FromRequest on a wrapper struct (e.g., ValidJson<T>), Ferrox will intercept the raw TCP bytes, deserialize them into JSON, and run the validator rules. If the rules fail, Ferrox intercepts the error and immediately returns an HTTP 400 Bad Request with a structured AppError::ValidationError, completely bypassing the Controller logic. \n\n---\n\n## 1. Philosophy / Purpose\n\nDocument the philosophy and core purpose of this component here.\n\n## 2. Architectural Layering\n\nExplain where this component sits within the Onion Architecture (e.g., Domain, Application, Infrastructure, or Presentation). \n\n## 4. Why it was designed this way\n\nExplain the historical context, trade-offs, and design rationale.\n\n## 6. Anti-Patterns\n\nList common mistakes, misconfigurations, and patterns to avoid when using this component.\n\n## 7. Pro-Tips / Best Practices\n\nProvide advanced tips, performance optimizations, and recommended patterns.