如何在Ruby on Rails中的请求之间保留查询字符串值？

Question

I'm coming up against one of those moments working with Rails when I feel that there must be a better way than what I'm ending up with.

I have four querystring parameters that I want to preserve across requests through various parts of a rails app - different controllers and actions, some rendered via javascript - so that the user ends up at a URL with the same querystring parameters that they started with.

I'm finding it hard to believe that the best way is through hidden form fields and manually adding the params back in as part of a redirect_to, or using session vars for each - it just seems to un-rails like.

Does anyone know of a better way to manage this?

Thanks!

Answer 1

In cases like this, I'll often use a helper function to create urls based on the current set of params. In other words, I'd define this:

def merge_params(p={})
  params.merge(p).delete_if{|k,v| v.blank?}
end

And then use it with url_for to create the urls for your forms and links. If you need to modify and of the params, just pass them into the merge:

# url for the current page
url_for(merge_params)

# url for a different action
url_for(merge_params(:controller => 'bar', :action => 'bar'))

# et cetera
url_for(merge_params(:action => 'pasta', :sauce => 'secret'))

This'll preserve existing params plus whatever overrides you merge in.

Answer 2

If you want to always preserve certain parameters accross every generated URL, you can implement a default_url_parameters method in your app.

This is poorly documented, but mentioned in the Rails 18n Guide

Implement in your application_controller.rb:

def default_url_options(*args)
  super.merge(
     :foo = params[:foo],
     :bar = params[:bar]
  )
end

Now every URL generated by Rails will include the current request's values for foo and bar (unless a url is being generated that specifies those specifically to be something else).

Answer 3

Please note this is not a rails solution but works for me in 80% cases. This is how I am able to achieve this with jQuery, obviously not the best approach. And I am unable to make it work past 2nd level of links:

function mergeGPS(){
  var lat = getParam('lat');//localStorage.getItem('lat');
  var lng = getParam('lng');//localStorage.getItem('lng');
  if(lat == null || lng == null){return false;}
    var links = jQuery("a");
    jQuery.each(links, function(y, lnk){
      //debugger;
     var uri = jQuery(lnk).attr('href') + "?lat="+lat+"&lng="+lng;
     jQuery(lnk).attr('href',uri); 
     //debugger;
    })
}

function getParam(name) {
    name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
    var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results === null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}

mergeGPS needs to be called on page load.