Ruby-on-rails 混合 ActiveRecord 查找条件
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Mixing ActiveRecord find Conditions
提问by Tony Pitale
I want to find records on a combination of created_on >= some date AND name IN some list of names.
我想在一些名称列表中查找 created_on >= some date AND name 组合的记录。
For ">=" I'd have to use sql condition. For "IN" I'd have to use a hash of conditions where the key is :name and the value is the array of names.
对于 ">=" 我必须使用 sql 条件。对于“IN”，我必须使用条件的散列，其中键是 :name，值是名称数组。
Is there a way to combine the two?
有没有办法将两者结合起来？
回答by Laurie Young
You can use named scopes in rails 2.1 and above
您可以在 rails 2.1 及更高版本中使用命名范围
Class Test < ActiveRecord::Base
named_scope :created_after_2005, :conditions => "created_on > 2005-01-01"
named_scope :named_fred, :conditions => { :name => "fred"}
end
then you can do
那么你可以做
Test.created_after_2005.named_fred
Or you can give named_scope a lambda allowing you to pass in arguments
或者你可以给 named_scope 一个 lambda 允许你传入参数
Class Test < ActiveRecord::Base
named_scope :created_after, lambda { |date| {:conditions => ["created_on > ?", date]} }
named_scope :named, lambda { |name| {:conditions => {:name => name}} }
end
then you can do
那么你可以做
Test.created_after(Time.now-1.year).named("fred")
回答by Josh Schwartzman
If you're using an older version Rails, Honza's query is close, but you need to add parentheses for the strings that get placed in the IN condition:
如果您使用的是旧版本的 Rails，Honza 的查询很接近，但您需要为放置在 IN 条件中的字符串添加括号：
Person.find(:all, :conditions => ["created_at > ? AND name IN (?)", date, names])
Using IN can be a mixed bag: it's fastest for integers and slowest for a list of strings. If you find yourself using just one name, definitely use an equals operator:
使用 IN 可能是一个混合包：它对于整数最快，对于字符串列表最慢。如果您发现自己只使用一个名称，请务必使用等号运算符：
Person.find(:all, :conditions => ["created_at > ? AND name = ?", date, name])
回答by ismaSan
The cool thing about named_scopes is that they work on collections too:
named_scopes 很酷的一点是它们也适用于集合：
class Post < ActiveRecord::Base
named_scope :published, :conditions => {:status => 'published'}
end
@post = Post.published
@posts = current_user.posts.published
回答by Sujoy Gupta
You can chain the whereclause:
您可以链接where子句：
Person.where(name: ['foo', 'bar', 'baz']).where('id >= ?', 42).first
Person.where(name: ['foo', 'bar', 'baz']).where('id >= ?', 42).first
回答by Sixty4Bit
For more on named_scopes see Ryan's announcementand the Railscast on named_scopes
有关named_scopes 的更多信息，请参阅Ryan 的公告和named_scopes 上的Railscast
class Person < ActiveRecord::Base
named_scope :registered, lambda { |time_ago| { :conditions => ['created_at > ?', time_ago] } }
named_scope :with_names, lambda { |names| { :conditions => { :names => names } } }
end
If you are going to pass in variables to your scopes you have to use a lambda.
如果要将变量传递给作用域，则必须使用 lambda。
回答by Honza
The named scopes already proposed are pretty fine. The clasic way to do it would be:
已经提出的命名范围非常好。这样做的经典方法是：
names = ["dave", "jerry", "mike"]
date = DateTime.now
Person.find(:all, :conidtions => ["created_at > ? AND name IN ?", date, names])
回答by Tony Pitale
I think I'm either going to use simple AR finders or Searchgasm.
我想我要么使用简单的 AR 查找器，要么使用Searchgasm。
