kmtr/atai

Atai is a getting value library.

Atai (値)

Atai is a getting value library.

Description

Someimes we want to get values from any places (environment variable, command line argument, DB, etc...). There are many library for its purpose, like os.Getenv. Atai is a wrapper of these function.

ValueProvider

ValueProvider is the core concept of this library. It is a type alias of the function (func() string). It can make abstraction that getting a value.

Sample

package main

import (
	"database/sql"
	"database/sql/driver"
	"flag"
	"fmt"
	"log"
	"os"

	"github.com/kmtr/atai"
)

var db *sql.DB

type DummyDB struct{}

func (db *DummyDB) Open(name string) (driver.Conn, error) {
	return nil, fmt.Errorf("DummyDB: open with `%s`", name)
}

func initialize(dbconn atai.ValueProvider) (err error) {
	sql.Register("dummydb", &DummyDB{})
	db, err = sql.Open("dummydb", dbconn())
	return
}

func main() {
	flag.String("db-conn", "", "Database connection string")
	flag.Parse()

	mvp := atai.MultipleValueProvider(
		atai.ValueFromFlag("db-conn"),
		atai.ValueFromEnv("DB_CONN"),
		atai.Value("default connection string"),
	)
	if err := initialize(mvp); err != nil {
		log.Printf("error: %v", err)
		os.Exit(1)
	}
	log.Printf("info: %v", db.Ping())
}

interface (ValueProviderHolder, KeyHolder, DefaultValueHolder, Explainer)

They are utility interfaces for using ValueProvider.

Sample

package main

import (
	"flag"
	"fmt"

	"github.com/kmtr/atai"
)

type KeyHolderAndExplainer interface {
	atai.KeyHolder
	atai.Explainer
}

func explain(vals ...KeyHolderAndExplainer) {
	for i, val := range vals {
		fmt.Printf("%d: %s, %s\n", i+1, val.Key(), val.Explain())
	}
}

func main() {
	flag.String("db-conn", "", "Database connection string")
	flag.Parse()

	fv := atai.NewFlagValue("db-conn")
	ev := atai.NewEnvValue("DB_CONN", "Database connection string")

	explain(fv, ev)
}