fiber/docs/api/state.md

id	title	sidebar_position
state	🗂️ State Management	8

The State Management provides a global key–value store for managing application dependencies and runtime data. This store is shared across the entire application and remains consistent between requests. It is implemented using Go’s sync.Map to ensure safe concurrent access.

State Type

State is a key–value store built on top of sync.Map. It allows storage and retrieval of dependencies and configurations in a Fiber application as well as thread–safe access to runtime data.

Definition

// State is a key–value store for Fiber's app, used as a global storage for the app's dependencies.
// It is a thread–safe implementation of a map[string]any, using sync.Map.
type State struct {
    dependencies sync.Map
}

Methods on State

Set

Set adds or updates a key–value pair in the State.

// Set adds or updates a key–value pair in the State.
func (s *State) Set(key string, value any)

Usage Example:

app.State().Set("appName", "My Fiber App")

Get

Get retrieves a value from the State.

func (s *State) Get(key string) (any, bool)

Usage Example:

value, ok := app.State().Get("appName")
if ok {
    fmt.Println("App Name:", value)
}

MustGet

MustGet retrieves a value from the State and panics if the key is not found.

func (s *State) MustGet(key string) any

Usage Example:

appName := app.State().MustGet("appName")
fmt.Println("App Name:", appName)

Has

Has checks if a key exists in the State.

func (s *State) Has(key string) bool

Usage Example:

if app.State().Has("appName") {
    fmt.Println("App Name is set.")
}

Delete

Delete removes a key–value pair from the State.

func (s *State) Delete(key string)

Usage Example:

app.State().Delete("obsoleteKey")

Reset

Reset removes all keys from the State.

func (s *State) Reset()

Usage Example:

app.State().Reset()

Keys

Keys returns a slice containing all keys present in the State.

func (s *State) Keys() []string

Usage Example:

keys := app.State().Keys()
fmt.Println("State Keys:", keys)

Len

Len returns the number of keys in the State.

// Len returns the number of keys in the State.
func (s *State) Len() int

Usage Example:

fmt.Printf("Total State Entries: %d\n", app.State().Len())

GetString

GetString retrieves a string value from the State. It returns the string and a boolean indicating a successful type assertion.

func (s *State) GetString(key string) (string, bool)

Usage Example:

if appName, ok := app.State().GetString("appName"); ok {
    fmt.Println("App Name:", appName)
}

GetInt

GetInt retrieves an integer value from the State. It returns the int and a boolean indicating a successful type assertion.

func (s *State) GetInt(key string) (int, bool)

Usage Example:

if count, ok := app.State().GetInt("userCount"); ok {
    fmt.Printf("User Count: %d\n", count)
}

GetBool

GetBool retrieves a boolean value from the State. It returns the bool and a boolean indicating a successful type assertion.

func (s *State) GetBool(key string) (value, bool)

Usage Example:

if debug, ok := app.State().GetBool("debugMode"); ok {
    fmt.Printf("Debug Mode: %v\n", debug)
}

GetFloat64

GetFloat64 retrieves a float64 value from the State. It returns the float64 and a boolean indicating a successful type assertion.

func (s *State) GetFloat64(key string) (float64, bool)

Usage Example:

if ratio, ok := app.State().GetFloat64("scalingFactor"); ok {
    fmt.Printf("Scaling Factor: %f\n", ratio)
}

GetUint

GetUint retrieves a uint value from the State.

func (s *State) GetUint(key string) (uint, bool)

Usage Example:

if val, ok := app.State().GetUint("maxConnections"); ok {
    fmt.Printf("Max Connections: %d\n", val)
}

GetInt8

GetInt8 retrieves an int8 value from the State.

func (s *State) GetInt8(key string) (int8, bool)

Usage Example:

if val, ok := app.State().GetInt8("threshold"); ok {
    fmt.Printf("Threshold: %d\n", val)
}

GetInt16

GetInt16 retrieves an int16 value from the State.

func (s *State) GetInt16(key string) (int16, bool)

Usage Example:

if val, ok := app.State().GetInt16("minValue"); ok {
    fmt.Printf("Minimum Value: %d\n", val)
}

GetInt32

GetInt32 retrieves an int32 value from the State.

func (s *State) GetInt32(key string) (int32, bool)

Usage Example:

if val, ok := app.State().GetInt32("portNumber"); ok {
    fmt.Printf("Port Number: %d\n", val)
}

GetInt64

GetInt64 retrieves an int64 value from the State.

func (s *State) GetInt64(key string) (int64, bool)

Usage Example:

if val, ok := app.State().GetInt64("fileSize"); ok {
    fmt.Printf("File Size: %d\n", val)
}

GetUint8

GetUint8 retrieves a uint8 value from the State.

func (s *State) GetUint8(key string) (uint8, bool)

Usage Example:

if val, ok := app.State().GetUint8("byteValue"); ok {
    fmt.Printf("Byte Value: %d\n", val)
}

GetUint16

GetUint16 retrieves a uint16 value from the State.

func (s *State) GetUint16(key string) (uint16, bool)

Usage Example:

if val, ok := app.State().GetUint16("limit"); ok {
    fmt.Printf("Limit: %d\n", val)
}

GetUint32

GetUint32 retrieves a uint32 value from the State.

func (s *State) GetUint32(key string) (uint32, bool)

Usage Example:

if val, ok := app.State().GetUint32("timeout"); ok {
    fmt.Printf("Timeout: %d\n", val)
}

GetUint64

GetUint64 retrieves a uint64 value from the State.

func (s *State) GetUint64(key string) (uint64, bool)

Usage Example:

if val, ok := app.State().GetUint64("maxSize"); ok {
    fmt.Printf("Max Size: %d\n", val)
}

GetUintptr

GetUintptr retrieves a uintptr value from the State.

func (s *State) GetUintptr(key string) (uintptr, bool)

Usage Example:

if val, ok := app.State().GetUintptr("pointerValue"); ok {
    fmt.Printf("Pointer Value: %d\n", val)
}

GetFloat32

GetFloat32 retrieves a float32 value from the State.

func (s *State) GetFloat32(key string) (float32, bool)

Usage Example:

if val, ok := app.State().GetFloat32("scalingFactor32"); ok {
    fmt.Printf("Scaling Factor (float32): %f\n", val)
}

GetComplex64

GetComplex64 retrieves a complex64 value from the State.

func (s *State) GetComplex64(key string) (complex64, bool)

Usage Example:

if val, ok := app.State().GetComplex64("complexVal"); ok {
    fmt.Printf("Complex Value (complex64): %v\n", val)
}

GetComplex128

GetComplex128 retrieves a complex128 value from the State.

func (s *State) GetComplex128(key string) (complex128, bool)

Usage Example:

if val, ok := app.State().GetComplex128("complexVal128"); ok {
    fmt.Printf("Complex Value (complex128): %v\n", val)
}

Generic Functions

Fiber provides generic functions to retrieve state values with type safety and fallback options.

GetState

GetState retrieves a value from the State and casts it to the desired type. It returns the cast value and a boolean indicating if the cast was successful.

func GetState[T any](s *State, key string) (T, bool)

Usage Example:

// Retrieve an integer value safely.
userCount, ok := GetState[int](app.State(), "userCount")
if ok {
    fmt.Printf("User Count: %d\n", userCount)
}

MustGetState

MustGetState retrieves a value from the State and casts it to the desired type. It panics if the key is not found or if the type assertion fails.

func MustGetState[T any](s *State, key string) T

Usage Example:

// Retrieve the value or panic if it is not present.
config := MustGetState[string](app.State(), "configFile")
fmt.Println("Config File:", config)

GetStateWithDefault

GetStateWithDefault retrieves a value from the State, casting it to the desired type. If the key is not present, it returns the provided default value.

func GetStateWithDefault[T any](s *State, key string, defaultVal T) T

Usage Example:

// Retrieve a value with a default fallback.
requestCount := GetStateWithDefault[int](app.State(), "requestCount", 0)
fmt.Printf("Request Count: %d\n", requestCount)

Comprehensive Examples

Example: Request Counter

This example demonstrates how to track the number of requests using the State.

package main

import (
    "fmt"

    "github.com/gofiber/fiber/v3"
)

func main() {
    app := fiber.New()

    // Initialize state with a counter.
    app.State().Set("requestCount", 0)

    // Middleware: Increase counter for every request.
    app.Use(func(c fiber.Ctx) error {
        count, _ := c.App().State().GetInt("requestCount")
        app.State().Set("requestCount", count+1)
        return c.Next()
    })

    app.Get("/", func(c fiber.Ctx) error {
        return c.SendString("Hello World!")
    })

    app.Get("/stats", func(c fiber.Ctx) error {
        count, _ := c.App().State().Get("requestCount")
        return c.SendString(fmt.Sprintf("Total requests: %d", count))
    })

    app.Listen(":3000")
}

Example: Environment–Specific Configuration

This example shows how to configure different settings based on the environment.

package main

import (
    "os"

    "github.com/gofiber/fiber/v3"
)

func main() {
    app := fiber.New()

    // Determine environment.
    environment := os.Getenv("ENV")
    if environment == "" {
        environment = "development"
    }
    app.State().Set("environment", environment)

    // Set environment-specific configurations.
    if environment == "development" {
        app.State().Set("apiUrl", "http://localhost:8080/api")
        app.State().Set("debug", true)
    } else {
        app.State().Set("apiUrl", "https://api.production.com")
        app.State().Set("debug", false)
    }

    app.Get("/config", func(c fiber.Ctx) error {
        config := map[string]any{
            "environment": environment,
            "apiUrl":      fiber.GetStateWithDefault(c.App().State(), "apiUrl", ""),
            "debug":       fiber.GetStateWithDefault(c.App().State(), "debug", false),
        }
        return c.JSON(config)
    })

    app.Listen(":3000")
}

Example: Dependency Injection with State Management

This example demonstrates how to use the State for dependency injection in a Fiber application.

package main

import (
    "context"
    "fmt"
    "log"

    "github.com/gofiber/fiber/v3"
    "github.com/redis/go-redis/v9"
)

type User struct {
    ID    int    `query:"id"`
    Name  string `query:"name"`
    Email string `query:"email"`
}

func main() {
    app := fiber.New()
    ctx := context.Background()

    // Initialize Redis client.
    rdb := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
        Password: "",
        DB:       0,
    })

    // Check the Redis connection.
    if err := rdb.Ping(ctx).Err(); err != nil {
        log.Fatalf("Could not connect to Redis: %v", err)
    }

    // Inject the Redis client into Fiber's State for dependency injection.
    app.State().Set("redis", rdb)

    app.Get("/user/create", func(c fiber.Ctx) error {
        var user User
        if err := c.Bind().Query(&user); err != nil {
            return c.Status(fiber.StatusBadRequest).SendString(err.Error())
        }

        // Save the user to the database.
        rdb, ok := fiber.GetState[*redis.Client](c.App().State(), "redis")
        if !ok {
            return c.Status(fiber.StatusInternalServerError).SendString("Redis client not found")
        }

        // Save the user to the database.
        key := fmt.Sprintf("user:%d", user.ID)
        err := rdb.HSet(ctx, key, "name", user.Name, "email", user.Email).Err()
        if err != nil {
            return c.Status(fiber.StatusInternalServerError).SendString(err.Error())
        }

        return c.JSON(user)
    })

    app.Get("/user/:id", func(c fiber.Ctx) error {
        id := c.Params("id")

        rdb, ok := fiber.GetState[*redis.Client](c.App().State(), "redis")
        if !ok {
            return c.Status(fiber.StatusInternalServerError).SendString("Redis client not found")
        }

        key := fmt.Sprintf("user:%s", id)
        user, err := rdb.HGetAll(ctx, key).Result()
        if err == redis.Nil {
            return c.Status(fiber.StatusNotFound).SendString("User not found")
        } else if err != nil {
            return c.Status(fiber.StatusInternalServerError).SendString(err.Error())
        }

        return c.JSON(user)
    })

    app.Listen(":3000")
}