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So, I'm pretty much a newbie at creating ruby methods. I've got the following method from a gem (meta_search), but I need to change the default behavior. Here's the method:

def sort_link(builder, attribute, *args) raise ArgumentError, "Need a MetaSearch::Builder search object as first param!" unless builder.is_a?(MetaSearch::Builder) attr_name = attribute.to_s name = (args.size > 0 && !args.first.is_a?(Hash)) ? args.shift.to_s : builder.base.human_attribute_name(attr_name) prev_attr, prev_order = builder.search_attributes['meta_sort'].to_s.split('.') current_order = prev_attr == attr_name ? prev_order : nil new_order = current_order == 'asc' ? 'desc' : 'asc' options = args.first.is_a?(Hash) ? args.shift : {} html_options = args.first.is_a?(Hash) ? args.shift : {} css = ['sort_link', current_order].compact.join(' ') html_options[:class] = [css, html_options[:class]].compact.join(' ') options.merge!( builder.search_key => builder.search_attributes.merge( 'meta_sort' => [attr_name, new_order].join('.') ) ) link_to [ERB::Util.h(name), order_indicator_for(current_order)].compact.join(' ').html_safe, url_for(options), html_options end

This method returns a sort link for a search. The output looks like this:

<a class="sort_link asc" href="/photos?search[meta_sort]=average_rating.desc">Best Photography ▲</a>

Here's the problem: this method assumes that you want to sort in ascending order on the first click, and descending order on the second. I want the opposite behavior. I see that I could change this...

new_order = current_order == 'asc' ? 'desc' : 'asc'

to this...

new_order = current_order == 'desc' ? 'asc' : 'desc'

...but that just reverses the situation. What I really need is to be able to specify an option and reverse the behavior if that option is passed.

So here's my problem: I don't really understand how the *args are passed. From what I can tell these lines are taking the option and html_option hashes for rails link_to method...

options = args.first.is_a?(Hash) ? args.shift : {} html_options = args.first.is_a?(Hash) ? args.shift : {}

What I'd like to do is add a custom option to the options hash, and if that option is defined reverse the sort equation. I tried to do this...

if defined? options[:sort_preference] && options[:sort_preference]==:desc new_order = current_order == 'desc' ? 'asc' : 'desc' options.delete(:sort_preference) else new_order = current_order == 'asc' ? 'desc' : 'asc' options.delete(:sort_preference) end

... but that didn't work, it just kept the standard behavior and passed :sort_preference into the URL like so:

<a class="sort_link asc" href="/photos?search[meta_sort]=average_rating.desc&sort_preference=desc">Best Photography ▲</a>

In the link above, sort_preference shouldn't appear in the URL, and search[meta_sort] should be average_rating.asc -- since the link shows the opposite of what rendered.

So, obviously, my attempt didn't work because I don't really understand what's going on in this method. What I'm hoping for in answer to this question is:

  • A little help understanding how *args works
  • An explanation of why my attempt to add an option to this method failed
  • An example of how to fix it

Thank you very much for taking a look!

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2 Answers 2

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*args just means that you can pass unlimited number of arguments. So this method needs 2 arguments first (builder & attribute) and then you could pass any number of args after that. Here is a description of what is going on in the method relating to the args:

  1. If the third argument passed to this method is not a hash, then it sets that arg as the name and removes it (args.shift), otherwise use the builder name.

  2. Then it looks at the next arg (which would be the 4th). If its a hash, then it sets options to that arg and deletes that arg, otherwise it sets it to empty hash.

  3. Then it looks at the next arg (5th arg). If its a hash, then it sets that as html_options and deletes that arg, otherwise html is set to {}.

Using args* can make calling the method a little cleaner (although the implementation in the method might not be). If you did not have a "name" to pass, instead of doing this:

sort_link(some_builder,some_attribute,nil,options)

you can do this:

sort_link(some_builder,some_attribute,options)

It does not force you to add a arg for name, if you don't have one.

So for your code to work, this method would need to take options as the 4th arg, and the options hash would need to contain :sort_preferences. What does the code look like that is calling sort_link? You need to insert this option into that hash before it gets to this method.

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2 Comments

To answer your question, the calling code is: = sort_link @search, :average_rating, "Best Photography", :sort_preference=>:desc
Ok, I get it now -- I needed to move options = args.first.is_a?(Hash) ? args.shift : {} up in order to make my if statement work. Once that line was moved up it works. Thank you for your explanation, that helped a lot!
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this method assumes that you want to sort in ascending order on the first click, and descending order on the second. I want the opposite behavior.

The meta_search gem supports this. It is not necessary to modify the gem's code. In your controller, after you have queried for your data, set the meta_sort attribute on the @search object to the field and sort order you would like. When the view loads, your data will be sorted as expected.

For example, in a Posts controller, you would do the following to set the default sort to the title field, descending:

def index @search = Post.search(params[:search]) @search.meta_sort ||= 'title.desc' @posts= @search.all end
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Hey thanks for this -- I still think the default behavior should be changeable inline rather than in the controller, but this is a good solution.

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