如何从 Rails Active Record 中的用户表创建数据数组？

Question

我有一个 User 表，其中包含full_name, email, phone, address, city, state, zip

我需要从 User 表中创建一个数组，其中包含这种格式的全名和电子邮件 ["user1.full_name, user1.email", "user2.full_name, user2.email" etc]

我在编写此查询时遇到问题。

这是我到目前为止

#create empty arrays
full_names = []
emails = []
#populate the full_names array
user_full_name = User.all
user_full_name.each{|x| full_names<<x.full_name}
#populate the emails array
user_email = User.all
user_email.each{|x| emails<<x.email}

#combine the two arrays
full_names.zip(emails)

但这给了我一个多维数组 [["full_name, email"], ["full_name, email"] 等]

我如何以 ["full_name, email", "full_name, email" 等格式获取它

Answer 1

User.all.map do |user|
  "#{user.full_name}, #{user.email}"
end

参见数组#map

---

提供更多关于此的信息。 当您使用ActiveRecord::QueryMethod （例如，您通过 ActiveRecord 进行查询）时，结果实际上不是一个数组，但它的行为类似于一个数组，通过在其上调用一个数组方法，您可以获取结果（请参阅ActiveRecord::关系）。 那是一口，但希望下面的例子会更清楚：

# This builds a query but doesn't actually fire it!
users = User.all

# chain onto the query - it still won't be fired yet
users = users.where.not(name: "Rick")

# see the query that will be run
users.to_sql

# check the type of this variable
users.class
# => ActiveRecord::Relation

# evaluates the query
users.count

# evaluates the query
users.to_a

# evaluates the query
users.any? { |user| user.email.nil? }

# evaluates the query
users.map { |user| user.full_name }

# evaluates the query
# does the same thing as the previous line
users.pluck(:first_name)

Answer 2

这里有两个^*可能的解决方案和它们对应的 SQL：

# SELECT "users"."full_name", "users"."email" FROM "users"
User.pluck('full_name', 'email').map{ |u| u.join(', ')}.flatten

# SELECT "users".* FROM "users"
User.all.map { |u| "#{u.full_name}, #{u.email}" }

所以， pluck比更有效all.map因为它只选择你想要的属性。

^*两者都在较早的回答中提到。