golangで日付を作る際のMonthのメモ。

整数直書きはOK.

package main

import (
	"fmt"
	"time"
)

func main() {
	d := time.Date(2015, 7, 1, 0, 0, 0, 0, time.UTC)
	fmt.Println(d) // 2015-07-01 00:00:00 +0000 UTC
}

int型の変数に入れて渡すとtime.Month型で渡せと言われる。

	m := 7
	d := time.Date(2015, m, 1, 0, 0, 0, 0, time.UTC)
	fmt.Println(d) // エラー cannot use m (type int) as type time.Month in argument to time.Date

time.Month型にCastして渡す。

	m := 7
	d := time.Date(2015, time.Month(m), 1, 0, 0, 0, 0, time.UTC)
	fmt.Println(d) // 2015-07-01 00:00:00 +0000 UTC

time.Month型を直接書くとこんなん。

	d := time.Date(2015, time.July, 1, 0, 0, 0, 0, time.UTC)
	fmt.Println(d) // 2015-07-01 00:00:00 +0000 UTC

ソース見たらこんな感じで定義されてる。

// A Month specifies a month of the year (January = 1, ...).
    77	type Month int
    78	
    79	const (
    80		January Month = 1 + iota
    81		February
    82		March
    83		April
    84		May
    85		June
    86		July
    87		August
    88		September
    89		October
    90		November
    91		December
    92	)