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collect & id

說明

  • collect > 從字面上就是收集的意思 > 是一個iterator，會複製一份array並且返回array > NOTE: The collect method is not the right way to do copying between arrays. There is another method called a clone which should be used to copy one array into another array.

  • &:id > id是資料庫的欄位名稱

  • collect(&:id) > 兩個合起來就是收集id的值

使用情境

使用方式

  • collect(&:id) > 取出欄位名稱為id的所有值，傳回陣列

例子

    # 抓出所有的值，並且收集返回它的name欄位的值
    def self.all_names
        find(:all).collect(&:name)
    end

    # 把 name 欄位取出，並改為小寫
    projects.collect(&:name).collect(&:downcase)

    Post.all.collect(&:title) #=> ["1 week from now", "Now", "1 week ago", "2 weeks ago"]
    Post.published.collect(&:title) #=> ["Now", "1 week ago", "2 weeks ago"]

    # Search combinations
    Post.search('1').collect(&:title) #=> ["1 week from now", "1 week ago"]
    Post.search('1').published.collect(&:title) #=> ["1 week ago"]
    Post.search('w').published_since(10.days.ago).collect(&:title) #=> ["Now", "1 week ago"]
    Post.search('w').order('created_at DESC').limit(2).collect(&:title) #=> ["2 weeks ago", "1 week ago"]

優點

參考資料