Ruby on Rails 開發從頭來（三十四）：Active Support 核心擴展詳解

Active Support 概覽

Active Support 是 Rails 核心擴展庫，擴充 Ruby 內建類別（Numeric, Time, String 等），提供大量實用方法，是 Rails 開發體驗流暢的關鍵基石。

數值擴展

位元組單位換算

20.bytes      # => 20
20.kilobytes  # => 20480
20.megabytes  # => 20971520
20.gigabytes  # => 21474836480
20.terabytes  # => 21990232555520

時間單位換算（以秒為基準）

20.minutes    # => 1200
20.hours      # => 72000
20.days       # => 1728000
20.weeks      # => 12096000
20.fortnights # => 24192000
20.months     # => 51840000  (近似：30天/月)
20.years      # => 630720000 (近似：365天/年)

奇偶數判斷

5.even?  # => false
5.odd?   # => true

時間擴展

Time 類別新增豐富的相對時間計算與邊界方法：

now = Time.now
now.ago(3600)                    # 1小時前
now.at_beginning_of_day          # 今天 00:00:00
now.at_beginning_of_week         # 本週一 00:00:00
now.at_beginning_of_month        # 本月1號 00:00:00
now.at_beginning_of_year         # 1月1號 00:00:00
now.change(:hour => 13)          # 今日 13:00:00
now.yesterday / now.tomorrow     # 昨天/明天同一時間
now.last_month / now.next_month  # 上/下個月同一天
now.months_ago(2) / months_since(2)
now.years_ago(2) / years_since(2)
now.seconds_since_midnight       # 今日經過秒數
now.midnight                     # 今日 00:00:00 (同 at_beginning_of_day)

時區支援

TimeZone 類別提供時區名稱、偏移量、標準時間/夏令時間轉換，支援 time_zone_select 表單輔助方法。

字串擴展

單複數轉換（內建不規則詞彙）

"cat".pluralize      # => "cats"
"cats".pluralize     # => "cats"
"erratum".pluralize  # => "errata"
"cats".singularize   # => "cat"
"errata".singularize # => "erratum"

大小寫與命名風格轉換

"active_record".camelize        # => "ActiveRecord"
"ActiveRecord".underscore       # => "active_record"
"active_record".titleize        # => "Active Record"
"ActiveRecord".demodulize       # => "ActiveRecord" (移除模組前綴)
"admin/user".tableize           # => "admin_users" (類別名→表名)
"admin_users".classify          # => "Admin::User" (表名→類別名)
"user_name".humanize            # => "User name" (欄位名→人類可讀)

其他實用方法

"  hello  ".squish       # => "hello" (移除首尾空白並壓縮中間多餘空白)
"hello".truncate(3)      # => "hel..."
"hello".starts_with?("he") # => true
"hello".ends_with?("lo")   # => true

陣列與雜湊擴展

[1,2,3].to_param        # => "1/2/3" (路由參數序列化)
{:a => 1}.to_param       # => "a=1" (查詢字串序列化)
[1,2,3].second           # => 2 (取第二個元素)
[1,2,3].from(1)          # => [2,3] (從索引1開始)
[1,2,3].to(1)            # => [1,2] (到索引1結束)
[1,2,3].in_groups_of(2)  # => [[1,2], [3,nil]] (分組)