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实例公共方法

except(*skips)

从查询中移除 skips 中指定的条件。

Post.order('id asc').except(:order)                  # removes the order condition
Post.where('id > 10').order('id asc').except(:where) # removes the where condition but keeps the order

来源: 显示 | 在 GitHub 上

# File activerecord/lib/active_record/relation/spawn_methods.rb, line 59
def except(*skips)
  relation_with values.except(*skips)
end

merge(other, *rest)

如果 other 是一个 ActiveRecord::Relation，则合并来自 other 的条件。如果 other 是一个数组，则返回一个表示结果记录与 other 的交集的数组。

Post.where(published: true).joins(:comments).merge( Comment.where(spam: false) )
# Performs a single join query with both where conditions.

recent_posts = Post.order('created_at DESC').first(5)
Post.where(published: true).merge(recent_posts)
# Returns the intersection of all published posts with the 5 most recently created posts.
# (This is just an example. You'd probably want to do this with a single query!)

Proc 将通过 merge 进行评估

Post.where(published: true).merge(-> { joins(:comments) })
# => Post.where(published: true).joins(:comments)

这主要用于在多个关联之间共享通用条件。

对于两个关系中都存在的条件，来自 other 的条件将优先。要查找两个关系的交集，请使用 QueryMethods#and。

来源: 显示 | 在 GitHub 上

# File activerecord/lib/active_record/relation/spawn_methods.rb, line 33
def merge(other, *rest)
  if other.is_a?(Array)
    records & other
  elsif other
    spawn.merge!(other, *rest)
  else
    raise ArgumentError, "invalid argument: #{other.inspect}."
  end
end

only(*onlies)

仅保留查询中 onlies 指定的条件，移除所有其他条件。

Post.order('id asc').only(:where)         # keeps only the where condition, removes the order
Post.order('id asc').only(:where, :order) # keeps only the where and order conditions

来源: 显示 | 在 GitHub 上

# File activerecord/lib/active_record/relation/spawn_methods.rb, line 67
def only(*onlies)
  relation_with values.slice(*onlies)
end