Send params{} hash to another method in same controller - ruby-on-rails

Question

I am working on very complex and dynamic form where I do lot of calls to various methods to render partials depending upon values chosen for drop downs using jQuery. Problem is that after filling the form if it fails validation the form loses all the filled in values upon re-load. I got around this by sending some specific values from params{} hash to methods for my partials on re-load. But it is very cumbersome and I have large number of elements in params hash. How can send the whole params{} to another method in the same controller using jQuery?
Ok I tried this in my form:
$.post("/collections/show_selected_media_fields",{media_type: $("#collections_controller_ev0_media_id option:selected").text(), parent_form_action: "<%=params[:action]%>",ev0_manufacturer_id:"<%=params[:collections_controller_ev0].inspect%>", }, function(data) {$("#show_selected_media_fields").html(data);});
It produces following string sent as parameter:
Parameters: {"ev0_manufacturer_id"=>"{"client_asset_id"=>"", "status_id"=>"6", "server_
name"=>"", "media_id"=>"11", "serial_number"=>"", "evidence_number&quot
;=>"qwe", "notes"=>"", "model"=>"", "manufacturer_id"=>"69&quot
;, "interface"=>"SATA", "obtained_from"=>"wr", "evidence_type_id"=>"1"}
", "media_type"=>"Server", "parent_form_action"=>"quick_save"}
how can I convert this raw string to a hash in controller?
{"client_asset_id"=>
needs to be converted to
{"client_asset_id"=>"",... etc}
===========
ok I tried Tom's method. That produces the params as a string in the following shape. I tried to convert it into hash by doing an eval on it. But it errors out.
{commit=>Save, ev1_current_location_id=>, collections_controller_ev1=>{file_system=>NTFS, obtained_from=>, evidence_number=>, interface=>SAT
A, size_unit=>GB, manufacturer_id=>, encryption_version=>, media_id=>3, size=>, evidence_type_id=>3, other_encryption=>, encryption_method=>
N/A, serial_number=>, model=>, encryption_key=>}, ev0_from_location_category=>, ev0_obtained_from_email_id=>, collections_controller_ev0=>{o
btained_from=>, evidence_number=>, media_id=>1, evidence_type_id=>1, status_id=>6}, custody_action=>Create, collection=>{acquired_by=>Amande
ep Singh, custodian_id=>12, matter_id=>58, location=>sa Nose, client_id=>11, software_version=>, collection_date_time=>Fri Nov 30 14:28:06 -
0800 2012, acquisition_method=>Direct Collection, notes=>, software_id=>1}, _method=>put, utf8=>Γ£ô, ev1_current_location_category=>, ev0_cu
rrent_location_category=>, add_working_copy=>No, ev1_obtained_from_email_id=>, authenticity_token=>3vyn6057DDIyfgTnbckeh5heRTIgcVBfxtY89Krfr
/c=, ev1_existing_artifact_type=>, ev0_from_location_id=>, action=>quick_save, ev1_from_location_id=>, ev1_from_location_category=>, ev0_cur
rent_location_id=>, controller=>collections}
using .to_json and HTMLEntities gem I have gotten to a point where I have the following string. I need to convert it back to params hash. How to?
{"utf8"=>"Γ£ô","collection"=>{"acquired_by"=>"Amandeep Singh","notes"=>"","matter_id"=>"58","software_id"=>"1","acquisition_method"=>"Direct
Collection","client_id"=>"11","custodian_id"=>"0","collection_date_time"=>"Fri Nov 30 15=>52=>12 -0800 2012","software_version"=>"","locati
on"=>"sa Nose"},"ev0_current_location_id"=>"","ev1_existing_artifact_type"=>"","ev1_obtained_from_email_id"=>"","custody_action"=>"Create","
action"=>"quick_save","ev0_current_location_category"=>"","ev1_from_location_category"=>"","_method"=>"put","ev0_obtained_from_email_id"=>""
,"ev0_from_location_category"=>"","ev1_current_location_category"=>"","commit"=>"Save","controller"=>"collections","authenticity_token"=>"3v
yn6057DDIyfgTnbckeh5heRTIgcVBfxtY89Krfr/c=","ev0_from_location_id"=>"","ev1_current_location_id"=>"","collections_controller_ev0"=>{"status_
id"=>"6","media_id"=>"9","obtained_from"=>"","evidence_number"=>"","evidence_type_id"=>"1"},"collections_controller_ev1"=>{"media_id"=>"3","
encryption_key"=>"","encryption_version"=>"","size"=>"","obtained_from"=>"","encryption_method"=>"N/A","model"=>"","evidence_number"=>"","ev
idence_type_id"=>"3","size_unit"=>"GB","other_encryption"=>"","interface"=>"SATA","file_system"=>"NTFS","serial_number"=>"","manufacturer_id
"=>""},"ev1_from_location_id"=>"","add_working_copy"=>"No"}
========== edit==========
I am using the following in my view.
JSON( params[:collections_controller_ev0])
It sends following quoted string to my controller.
{"evidence_number":"","notes":"","size":"","model":"","evidence_type_id":"1","media_id":"1","obtained_from":"","status_id":"6","manufacturer_id":"","size_unit":"GB"}
I convert it into valid JSON string as below using gsub('"','"'). The output is a VALID JSON string as validated by http://jsonlint.com/ shown below.
{"evidence_number":"","notes":"123","size":"123","model":"123","evidence_type_id":"1","media_id":"1","obtained_from":"","status_id":"6","manufacturer_id":"69","size_unit":"GB"}
JSON.parse works without error on this string but does not produce a properly formed hash. It produces following:
notes123evidence_numbersize123model123evidence_type_id1media_id1obtained_fromstatus_id6size_unitGBmanufacturer_id69
Can someone please tell me how to correct this?

Answer 1

Try <%=raw params[:action]%> and <%=raw params[:collections_controller_ev0]%> instead
I think it will work fine.
$.post("/collections/show_selected_media_fields",{media_type: $("#collections_controller_ev0_media_id option:selected").text(), parent_form_action: <%=raw params[:action]%>,ev0_manufacturer_id:<%=raw params[:collections_controller_ev0].inspect%>, }, function(data) {$("#show_selected_media_fields").html(data);});

Answer 2

params is basically a hash. So you can use .to_json on it. Then in your controller you can convert it from JSON to a hash with JSON.parse().
It's generally a much better idea to use JSON if you're going to be dealing with it in Javascript or HTML at all.

Answer 3

The method showed in my last edit works! it produces correct hash.