blocks|key|915542|text|嗯，你想要使用的最好的方法可以是在两个动作中传播它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|915543|def+index
+++@post+=+Post.all
end

def+get
++@post+=+Post.where("author=?",+params[:author_id])
end|code-block|syntax|javascript|915544|如果你考虑一个RESTful应用程序接口，索引就更有意义了，索引意味着列出所有内容，然后获取(或显示)请求的接口并显示它！|915545|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Mmmh, the best approach you want to use can be to spread this in 2 actions

<pre><code>def index
 @post = Post.all
end

def get
 @post = Post.where("author=?", params[:author_id])
end
</code></pre>

IMHO it has more sense if you think about a RESTful API, index means to list all and get (or show) to fetch the requested one and show it!

blocks|key|699470|text|像这样的东西可以工作吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|699471|def+get
++raise+"Bad+parameters...why+are+you+doing+this?"+unless+params[:filter].is_a?(Hash)
++@post+=+Post.where(params[:filter])
end|code-block|syntax|javascript|699472|然后你可以这样做：?filterauthor_id=1&filterpost_date=..。等。|699473|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Would something like this work?

<pre><code>def get
 raise "Bad parameters...why are you doing this?" unless params[:filter].is_a?(Hash)
 @post = Post.where(params[:filter])
end
</code></pre>

Then you can do something like:
 ?filter[author_id]=1&amp;filter[post_date]=... etc.

blocks|key|915589|text|您应该使用嵌套资源对url进行建模。预期的url将是/authors/1/post。将作者视为资源。阅读本指南中关于嵌套资源的内容：http://guides.rubyonrails.org/routing.html+(滚动到2.7+-嵌套资源)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|915590|entityMap|0|LINK|mutability|MUTABLE|url|http://guides.rubyonrails.org/routing.html^0|1U|16|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

You should model url using nested resources. The expected url would be /authors/1/posts. Think of authors as resources. Read about nested resources in this guide: <a href="http://guides.rubyonrails.org/routing.html" rel="nofollow">http://guides.rubyonrails.org/routing.html</a> (scroll to 2.7 - Nested Resources).

blocks|key|915610|text|这样如何：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|915611|def+index
++author_id+=+params[:author_id]

++@posts+=+Post.scoped

++@post+=+@post.where(:author_id+=>+author_id)+if+author_id.present?

++@post+=+@post.where(:some_other_condition+=>+some_other_value)+if+some_other_value.present?
end|code-block|syntax|javascript|915612|Post.scoped本质上是一个延迟加载的等价于Post.all+(因为Post.all立即返回一个数组，而Post.scoped只返回一个关系对象)。只有在视图中实际尝试迭代该查询(通过调用.each)之后，才会执行该查询。|offset|length|style|CODE|915613|entityMap^0|0|0|0|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

How about:

<pre><code>def index
 author_id = params[:author_id]

 @posts = Post.scoped

 @post = @post.where(:author_id =&gt; author_id) if author_id.present?

 @post = @post.where(:some_other_condition =&gt; some_other_value) if some_other_value.present?
end
</code></pre>

<code>Post.scoped</code> is essentially a lazy loaded equivalent to Post.all (since Post.all returns an array
immediately, while Post.scoped just returns a relation object). This query won't be executed until 
you actually try to iterate over it in the view (by calling .each).

blocks|key|699582|text|这个问题已经很老了，但它在2019年仍然在google中出现得很多，而且一些早期的答案已经被弃用，所以我想我应该分享一个可能的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|699583|在模型中，引入一些作用域，并对传递的参数是否存在进行测试：|699584|class+Post
++++scope+:where_author_ids,+->(ids){+where(author_id:+ids.split(‘,’))+if+ids+}
++++scope+:where_topic_ids,++->(ids){+where(topic_id:++ids.split(‘,’))+if+ids+}|code-block|syntax|javascript|699585|然后在控制器中，你可以想放多少过滤器就放多少，例如：|699586|def+list
++++@posts+=+Post.where_author_ids(params[:author_ids])
+++++++++++++++++.where_topic_ids(params[:topic_ids])++++++++++++++++++++++++++++++++++
+++++++++++++++++.where_other_condition_ids(params[:other_condition_ids])
+++++++++++++++++.order(:created_at)|699587|然后，该参数可以是单个值或逗号分隔的值列表，这两种方法都可以正常工作。|699588|如果参数不存在，它就会跳过where子句，不会根据特定条件进行过滤。如果参数存在，但它的值是空字符串，那么它将“过滤掉”所有内容。|699589|当然，这种解决方案并不适用于所有情况。如果你有一个打开了多个过滤器的视图页面，但在第一次打开时，你想要显示所有数据，而不是没有数据，直到你按下“提交”按钮或类似的按钮(就像这个控制器一样)，那么你就必须稍微调整一下。|699590|我已经尝试过SQL注入，在我看来，rails在保证一切安全方面做得很好。|699591|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

This question is pretty old but it still comes up high in google in 2019, and also some earlier answers have been deprecated, so I thought I would share a possible solution.

In the model introduce some scopes with a test for the existence of the parameter passed:

<pre><code>class Post
 scope :where_author_ids, -&gt;(ids){ where(author_id: ids.split(‘,’)) if ids }
 scope :where_topic_ids, -&gt;(ids){ where(topic_id: ids.split(‘,’)) if ids }
</code></pre>

Then in the controller you can just put as many filters in as you wish e.g:

<pre><code>def list
 @posts = Post.where_author_ids(params[:author_ids])
 .where_topic_ids(params[:topic_ids]) 
 .where_other_condition_ids(params[:other_condition_ids])
 .order(:created_at)
</code></pre>

The parameter can then be a single value or a comma separated list of values, both work fine.

If a param doesn’t exist it simply skips that where clause and doesn’t filter for that particular criteria. If the param exists but its value is an empty string then it will ‘filter out’ everything.

This solution won’t suit every circumstance of course. If you have a view page with several filters on, but upon first opening you want to show all your data instead of no data until you press a ‘submit’ button or similar (as this controller would) then you will have to tweak it slightly. 

I’ve had a go at SQL injecting this and rails seems to do a good job of keeping everything secure as far as I can see.

What's the best way to construct a where clause using Rails ActiveRecord? For instance, let's say I have a controller action that returns a list of blog posts:

<pre><code>def index
 @posts = Post.all
end
</code></pre>

Now, let's say I want to be able to pass in a url parameter so that this controller action only returns posts by a specific author:

<pre><code>def index
 author_id = params[:author_id]

 if author_id.nil?
 @posts = Post.all
 else
 @posts = Post.where("author = ?", author_id)
 end
end
</code></pre>

This doesn't feel very DRY to me. If I were to add ordering or pagination or worse yet, more optional URL query string params to filter by, this controller action would get very complicated.

Constructing a Rails ActiveRecord where clause

使用Rails ActiveRecord构造where子句的最佳方式是什么？例如，假设我有一个返回博客帖子列表的控制器操作：def index  @posts = Post.allend现在，假设我希望能够传递一个url参数，以便这个控制器操作只返回特定作者的帖子：def index  author_id = para...

问构造Rails ActiveRecord where子句
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