9.6 KiB
State Management
This document details the state management functionality provided by Fiber, a thread-safe global key-value store used to store application dependencies and runtime data. The implementation is based on Go's sync.Map ensuring concurrency safety.
Below is the detailed description of all public methods and usage examples.
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 in order to be used as a global storage for the app's dependencies.
// It's 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.
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)
GetString
GetString retrieves a string value from the State. It returns the string and a boolean indicating 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 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 successful type assertion.
func (s *State) GetBool(key string) (value, ok 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 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)
}
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 resets the State by removing all keys.
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.
func (s *State) Len() int
Usage Example:
fmt.Printf("Total State Entries: %d\n", app.State().Len())
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 casted 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 := fiber.GetStateWithDefault(app.State(), "requestCount", 0)
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 := fiber.GetStateWithDefault(c.App().State(), "requestCount", 0)
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(app.State(), "apiUrl", ""),
"debug": fiber.GetStateWithDefault(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](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](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")
}