Fiber Ctx: Context Methods vs Express.js

In this tutorial, you'll learn about Fiber Ctx: Context Methods vs Express.js. We cover key concepts, practical examples, and best practices.

Fiber context usage -- Learn Fiber's Ctx methods for routing, parameters, body parsing, and response writing.

The Problem

Fiber's Ctx API mirrors Express.js but uses different method names. From Express you expect req.params.id but Fiber uses c.Params("id").

Wrong

app := fiber.New()
app.Get("/users/:id", func(c *fiber.Ctx) error {
    return c.JSON(fiber.Map{
        "id": c.Params("id"),
        "name": c.Query("name"),
    })
})

Output:

$ curl "http://localhost:8080/users/42?name=John"
{"id":"42","name":"John"}

Right

app.Get("/", func(c *fiber.Ctx) error {
    c.Set("X-Custom", "value")
    c.Status(201)
    return c.SendString("Hello!")
})

Output:

$ curl http://localhost:8080/
Hello!

Prevention

• Use c.Params("key") for route parameters
• Use c.Query("key") for query parameters
• Use c.BodyParser(&struct) for request body binding
• Use c.JSON(data) for JSON responses
• Use c.Status(code) to set status code

Common Mistakes with fiber ctx

1. Using head and tail instead of pattern matching, causing runtime errors on empty lists
2. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks
3. Using return to exit a function early instead of wrapping a pure value in the monad

These mistakes appear frequently in real-world GO code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

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