如何使用或不使用Rails示波器？

Question

I have a two scopes in my user model:

scope :hard_deactivated, where(:hard_deactivated => true)
scope :soft_deactivated, where(:soft_deactivated => true)

So far so good

OR

I want to create a scope :deactivated, which will include all users where hard_deactivated is true OR soft deactivated is true. Obviously I could just do this:

scope :deactivated, where("hard_deactivated = ? or soft_deactivated = ?", true, true)

but this does not feel very dry.

NOT

Also I would like to create an inverse scope :not_hard_deactivated. I could do this:

scope :not_hard_deactivated, where(:hard_deactivated => false)

but again, this feels bad, especially if my scope becomes more complex. There should be some way or warpping the SQL generated by the previous scope in a not clause.

Answer 1

Use an arel table:

hard_deactivated_true = arel_table[:hard_deactivated].eq(true)
soft_deactivated_true = arel_table[:soft_deactivated].eq(true)

scope :deactivated, where(hard_deactivated_true.and(soft_deactivated_true))
scope :not_hard_deactivated, where(hard_deactivated_true.not)

See: Is it possible to invert a named scope in Rails3?

Answer 2

For the "NOT" part, you can do something like this:

extend ScopeUtils

positive_and_negative_scopes :deactivated do |value|
  where(:hard_deactivated => value)
end

And implement this method in a separate module:

module ScopeUtils
  def positive_and_negative_scopes(name)
    [true, false].each do |filter_value|
      prefix = ("not_" if filter_value == false)
      scope :"#{prefix}#{name}", yield(filter_value)
    end
  end
end

Regarding the "OR" case, you might be something similar, depending on what your recurring pattern is. In the simple example above it's not worth it, as doesn't help readability.

scopes_with_adjectives_and_negatives :deactivated, [:soft, :hard]

module ScopeUtils
  def scopes_with_adjectives_and_negatives(name, kinds)
    kinds.each do |kind|
      positive_and_negative_scopes name do |filter_value|
        where("#{kind}_#{name}" => filter_value)
      end
    end
    scope :"#{name}", where(kinds.map{|kind| "#{kind}_#{name} = ?"}.join(" OR "), true, true)
    scope :"not_#{name}", where(kinds.map{|kind| "#{kind}_#{name} = ?"}.join(" AND "), false, false)
  end
end

Answer 3

您应该在where方法中使用sql片段（如您的第二个示例中），或在squeel等更多的“糖”类宝石中使用