ruby-on-rails - 有没有一种方法可以将 rails 中的值设置为 nil 并保存？

Question

我想到的是我可以说的话:

e = Foo.new
e.bar = "hello"
e.save
e.reload
e.bar.nil!
e.reload
e.bar.nil?  => true

有点像#touch，但设置为零并保存。

编辑

非常抱歉，伙计们。我的意思是:

e = Foo.new
e.bar = "hello"
e.save
e.reload
e.bar.nil!
e.reload
e.bar.nil?  => true

Answer 1

也许是这样的:

module ActiveRecord
  class Base
    def nil!(*names)
      unless persisted?
        raise ActiveRecordError, <<-MSG.squish
          cannot nil on a new or destroyed record object. Consider using
          persisted?, new_record?, or destroyed? before nilling
        MSG
      end

      unless names.empty?
        changes = {}

        names.each do |column|
          column = column.to_s
          changes[column] = write_attribute(column, nil)
        end

        primary_key = self.class.primary_key
        scope = self.class.unscoped.where(primary_key => _read_attribute(primary_key))

        if locking_enabled?
          locking_column = self.class.locking_column
          scope = scope.where(locking_column => _read_attribute(locking_column))
          changes[locking_column] = increment_lock
        end

        clear_attribute_changes(changes.keys)
        result = scope.update_all(changes) == 1

        if !result && locking_enabled?
          raise ActiveRecord::StaleObjectError.new(self, "nil")
        end

        @_trigger_update_callback = result
        result
      else
        true
      end      
    end
  end
end

将其放入初始化程序中，它会让您使用 Comment.last.nil!(:title) 清空评论的标题。