Goのsortパッケージでtime.Timeの要素を基にソートする
時間でソートしたい
小ネタ。
sort.Sliceでソート
Go1.8以降でならsort.Sliceを使ったシンプルな方法でソートできる。
Go 1.8 Release Notes - The Go Programming Language
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| package main | |
| import ( | |
| "fmt" | |
| "sort" | |
| "time" | |
| ) | |
| type FileInfo struct { | |
| FileName string | |
| CreatedAt time.Time | |
| } | |
| func s_print(s []FileInfo, title string) { | |
| fmt.Println(title) | |
| for i, v := range s { | |
| fmt.Printf("%d: %s, %s\n", i, v.FileName, v.CreatedAt.Format(time.RFC3339)) | |
| } | |
| } | |
| func main() { | |
| s := []FileInfo{ | |
| {"file_middle", time.Now().Add(12 * time.Hour)}, | |
| {"file_first", time.Now()}, | |
| {"file_last", time.Now().Add(24 * time.Hour)}, | |
| } | |
| s_print(s, "Before") | |
| // Before | |
| // 0: file_middle, 2020-08-09T01:25:46Z | |
| // 1: file_first, 2020-08-08T13:25:46Z | |
| // 2: file_last, 2020-08-09T13:25:46Z | |
| // sort by newest to oldest | |
| sort.Slice(s, func(i, j int) bool { | |
| return s[i].CreatedAt.After(s[j].CreatedAt) | |
| }) | |
| s_print(s, "Sort by newest to oldest") | |
| // Sort by newest to oldest | |
| // 0: file_last, 2020-08-09T13:25:46Z | |
| // 1: file_middle, 2020-08-09T01:25:46Z | |
| // 2: file_first, 2020-08-08T13:25:46Z | |
| // sort by oldest to newest | |
| sort.Slice(s, func(i, j int) bool { | |
| return s[i].CreatedAt.Before(s[j].CreatedAt) | |
| }) | |
| s_print(s, "Sort by oldest to newest") | |
| // Sort by oldest to newest | |
| // 0: file_first, 2020-08-08T13:25:46Z | |
| // 1: file_middle, 2020-08-09T01:25:46Z | |
| // 2: file_last, 2020-08-09T13:25:46Z | |
| } |
Len,Swap,Lessを使う
Go1.8より前、もしくは独自のソートを行いたい場合はsort.Sortのinterfaceを満たすためにLen,Swap,Lessを用意する。