Ruby-on-rails 带参数的 Rails 4 范围
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/23412719/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Rails 4 scope with argument
提问by Victor
Upgrading Rails 3.2. to Rails 4. I have the following scope:
升级 Rails 3.2。到 Rails 4。我有以下范围：
# Rails 3.2
scope :by_post_status, lambda { |post_status| where("post_status = ?", post_status) }
scope :published, by_post_status("public")
scope :draft, by_post_status("draft")
# Rails 4.1.0
scope :by_post_status, -> (post_status) { where('post_status = ?', post_status) }
But I couldn't find out how to do the 2nd and 3rd lines. How can I create another scope from the first scope?
但我不知道如何做第 2 行和第 3 行。如何从第一个范围创建另一个范围？
回答by Зелёный
Very simple, just same lambda without arguments:
非常简单，就是没有参数的相同 lambda：
scope :by_post_status, -> (post_status) { where('post_status = ?', post_status) }
scope :published, -> { by_post_status("public") }
scope :draft, -> { by_post_status("draft") }
or more shorted:
或更短：
%i[published draft].each do |type|
scope type, -> { by_post_status(type.to_s) }
end
回答by wvandaal
From the Rails edge docs
"Rails 4.0 requires that scopes use a callable object such as a Proc or lambda:"
“Rails 4.0 要求作用域使用可调用对象，例如 Proc 或 lambda：”
scope :active, where(active: true)
# becomes
scope :active, -> { where active: true }
With this in mind, you can easily rewrite you code as such:
考虑到这一点，您可以轻松地重写代码：
scope :by_post_status, lambda { |post_status| where('post_status = ?', post_status) }
scope :published, lambda { by_post_status("public") }
scope :draft, lambda { by_post_status("draft") }
In the event that you have many different statuses that you wish to support and find this to be cumbersome, the following may suit you:
如果您有许多不同的状态想要支持并且觉得这很麻烦，那么以下可能适合您：
post_statuses = %I[public draft private published ...]
scope :by_post_status, -> (post_status) { where('post_status = ?', post_status) }
post_statuses.each {|s| scope s, -> {by_post_status(s.to_s)} }
