I am facing an issue with accessing a particular variable of a method say A , in another method say B in the controller.. The size of the object(variable) is too big since it contains the results of a service call made.. My usecase is like on selecting an option from a drop down box, it redirects to a method B in controller and the same object(variable) should be parsed. How can I access the variable in the other method?
I tried storing in a cookie and since the size is too big I am getting Cookie Overflow exception. I am not using a DB. So I guess using memcache won't work. Also tried storing it as hidden field in view and passed its value as a data through ajax call. But I am getting it as a string. Tried to specify datatype as json and several other ways.. but of no use..Using ##var also din work..Not sure why..
Code:
On change of the drop down:
$(document).ready(function(){
$('#filter_service').change(function() {
$.ajax({type: "GET",
url: "/device_troubleshootings/query_operation",
data: { filter_service: $('# filter_service').val()},
});
});
});
Service call:
def log_results
//Service call
#get_log_results = LogQueryService.client.get_logs(Com::Amazon::Logqueryservice::DeviceSerialNumberQuery.new(:search_text => # search , :index => 'dms', :index_type => '_all', :from_time_stamp => #from_time_stamp, :to_time_stamp => #to_time_stamp))
#dsn_result = #get_log_results.logs_result_obj_list
end
Here, I am trying to access #dsn_result object in "/device_troubleshootings/query_operation” method.
Please suggest me ways to access the variable.
MVC
I think you're getting confused with how Rails should work
Remember, Rails (which is just a framework for Ruby) is built on the "MVC" programming pattern. This means each time you send a request to your Rails application, it has to be handled by a single controller#action which you will then allow you to pull the relevant data from your models
The problem you have is you're trying to load multiple controller methods, and pass the same data to both. This might work in Ruby, but not Rails (Rails is stateless):
--
Model
The correct way to handle this type of setup is by creating another request for your application, which will load another controller#action, allowing you to access the data you need
As demonstrated by the MVC diagram above, each time you send a request to Rails, it's basically a new request. This means that unless you've persisted your data in the likes of a cookie, you'll need to load the data from the model.
The problem you have is you're trying to store an entire data-set in the front-end of your system. This issue is very bad, as not only is it inefficient, but it goes against the MVC pattern completely.
You'll be much better storing the bare-minimum data set you need in the front-end (ids or similar), which you will then be able send to your controller via ajax; building a new data-set from
--
Class Variables
You mentioned you tried to declare some ##class variables to no avail. The problem with this is that the class vars will only be available for an instance of a class.
As mentioned, since Rails is stateless, the class variables won't persist between requests (how can they?). I think you know this already, considering you've been trying to use cookies to store your data
The way to resolve this is to rebuild the data each time from the model (as detailed above)
Solution
The solution for you is to "go stateless"
Here's how:
Treat Method A and Method B as completely separate "ACTIONS"
When using these actions, you need to consider the smallest piece of data to pass between the two
To load Method B, you need to send a new request from your browser (as if you've never loaded Method A before)
Your method_a can be handled in the "standard" way:
#config/routes.rb
resources :your_controller do
collection do
get :method_a
get :method_b
end
end
This will mean that you can load method_a relatively simply:
#app/controllers/your_controller.rb
Class YourController < ApplicationController
def method_a
#get_log_results = LogQueryService.client.get_logs(Com::Amazon::Logqueryservice::DeviceSerialNumberQuery.new(:search_text => # search , :index => 'dms', :index_type => '_all', :from_time_stamp => #from_time_stamp, :to_time_stamp => #to_time_stamp))
#dsn_result = #get_log_results.logs_result_obj_list
end
end
As you know, the #dsn_result will not persist through to the next request.
There are two ways to resolve this (set a CONSTANT -- if you're pulling from an API, this will give you a single call -- or use a before_action to set the variable for as many actions as you need). I'll detail both for you:
#app/controllers/your_controller.rb
Class YourController < ApplicationController
before_action :set_log_data
def method_a
end
def method_b
end
private
def set_log_data
#get_log_results = LogQueryService.client.get_logs(Com::Amazon::Logqueryservice::DeviceSerialNumberQuery.new(:search_text => # search , :index => 'dms', :index_type => '_all', :from_time_stamp => #from_time_stamp, :to_time_stamp => #to_time_stamp))
#dsn_result = #get_log_results.logs_result_obj_list
end
end
This will work if you pull data from your own data-set (using the models), however, the better way to do this in your case will likely be to set a constant (considering, of course, that you don't want the data to change):
#config/initializers/dsn_result.rb
get_log_results = LogQueryService.client.get_logs(Com::Amazon::Logqueryservice::DeviceSerialNumberQuery.new(:search_text => # search , :index => 'dms', :index_type => '_all', :from_time_stamp => #from_time_stamp, :to_time_stamp => #to_time_stamp))
DSN_RESULT = get_log_results.logs_result_obj_list
In my case I solved with global variable $my_global_var
So my files look like this
routes.rb
Rails.application.routes.draw do
resources :pages
root 'pages#index'
post 'pages/test'
end
pages_controller.rb
class PagesController < ApplicationController
def firstaction
$my_global_var = "My global var"
puts $my_global_var
end
def secondaction
puts $my_global_var
end
end
index.html.erb
<%= button_to 'Test', pages_test_path, method: :post %>
I am implementing a REST API which is versioned(like Twitter API), so based on version in request, I need to render template specific to the version, for example, if the client requests:
http://www.foo.com/api/v1/posts.json
I'd like to have the controller render:
posts/index.v1.json.erb
but if the client requests
http://www.foo.com/api/v2/posts.json
I'd like to have the controller render:
posts/index.v2.json.erb
and so on.
the version number in URL will be put in params hash in route.rb.
I want to do this in a reusable way, so it's not acceptable to repeat the logic in specific controller action.
I have tried view resolver, however it doesn't have access to request so there is no way I can pass the version number to resolver.
is there any way to accomplish this?
Thank you!
-Xiaotian
You can specify the version number in your routes.rb like:
map.connect '/api/:version/posts', :controller => :api, :action => :index, :version => :version
Then you would have access to the version in your controller via params[:version] and can handle it appropriately.
I think I would suggest making a separate controller for each version, maybe in the same module
Api::VersionOneConroller
Api::VersionTwoConroller
or something like that, I am not familiar with your whole app so I cannot say whether that will work, buts its something to consider.
------------update-------------
if the difference in versions in only in output foramtting or somehting, and all the actions do the same thing you could add after filters
class ExampleContrller < ApplicationController
after_filter :manage_versions
...
end
ApplicationController < ActionController::Base
protected
def manage_versions
case params[:version]
when '1.0'
#response to xml
when '1.2'
#response to json
else
# err or default to one
end
end
end
something like that could work
read more about filters here http://rails.rubyonrails.org/classes/ActionController/Filters/ClassMethods.html
I'm using this code (taken from here) in ApplicationController to detect iPhone, iPod Touch and iPad requests:
before_filter :detect_mobile_request, :detect_tablet_request
protected
def detect_mobile_request
request.format = :mobile if mobile_request?
end
def mobile_request?
#request.subdomains.first == 'm'
request.user_agent =~ /iPhone/ || request.user_agent =~ /iPod/
end
def detect_tablet_request
request.format = :tablet if tablet_request?
end
def tablet_request?
#request.subdomains.first == 't'
request.user_agent =~ /iPad/
end
This allows me to have templates like show.html.erb, show.mobile.erb, and show.tablet.erb, which is great, but there's a problem: It seems I must define every template for each mime type. For example, requesting the "show" action from an iPhone without defining show.mobile.erb will throw an error even if show.html.erb is defined. If a mobile or tablet template is missing, I'd like to simply fall back on the html one. It doesn't seem too far fetched since "mobile" is defined as an alias to "text/html" in mime_types.rb.
So, a few questions:
Am I doing this wrong? Or, is there a better way to do this?
If not, can I get the mobile and tablet mime types to fall back on html if a mobile or tablet file is not present?
If it matters, I'm using Rails 3.0.1. Thanks in advance for any pointers.
EDIT: Something I forgot to mention: I'll eventually be moving to separate sub-domains (as you can see commented out in my example) so the template loading really needs to happen automatically regardless of which before_filter has run.
Possible Duplicate of Changing view formats in rails 3.1 (delivering mobile html formats, fallback on normal html)
However, I struggled with this exact same problem and came up with a fairly elegant solution that met my needs perfectly. Here is my answer from the other post.
I think I've found the best way to do this. I was attempting the same thing that you were, but then I remembered that in rails 3.1 introduced template inheritance, which is exactly what we need for something like this to work. I really can't take much credit for this implementation as its all laid out there in that railscasts link by Ryan Bates.
So this is basically how it goes.
Create a subdirectory in app/views. I labeled mine mobile.
Nest all view templates you want to override in the same structure format that they would be in the views directory. views/posts/index.html.erb -> views/mobile/posts/index.html.erb
Create a before_filter in your Application_Controller and do something to this effect.
before_filter :prep_mobile
def is_mobile?
request.user_agent =~ /Mobile|webOS|iPhone/
end
def prep_mobile
prepend_view_path "app/views/mobile" if is_mobile?
end
Once thats done, your files will default to the mobile views if they are on a mobile device and fallback to the regular templates if a mobile one is not present.
You need to do several things to wire this up, but the good news is that Rails 3 actually makes this a lot simpler than it used to be, and you can let the router do most of the hard work for you.
First off, you need to make a special route that sets up the correct mime type for you:
# In routes.rb:
resources :things, :user_agent => /iPhone/, :format => :iphone
resources :things
Now you have things accessed by an iphone user agent being marked with the iphone mime type. Rails will explode at you for a missing mime type though, so head over to config/initializers/mime_types.rb and uncomment the iphone one:
Mime::Type.register_alias "text/html", :iphone
Now you're mime type is ready for use, but your controller probably doesn't yet know about your new mime type, and as such you'll see 406 responses. To solve this, just add a mime-type allowance at the top of the controller, using repsond_to:
class ThingsController < ApplicationController
respond_to :html, :xml, :iphone
Now you can just use respond_to blocks or respond_with as normal.
There currently is no API to easily perform the automatic fallback other than the monkeypatch or non-mime template approaches already discussed. You might be able to wire up an override more cleanly using a specialized responder class.
Other recommended reading includes:
https://github.com/plataformatec/responders
http://www.railsdispatch.com/posts/rails-3-makes-life-better
Trying removing the .html from the .html.erb and both iPhone and browser will fallback to the common file.
I have added a new answer for version 3.2.X. This answer is valid for <~ 3.0.1.
I came to this question while looking to be able to have multiple fallbacks on the view. For example if my product can be white-labeled and in turn if my white-label partner is able to sell sponsorship, then I need a cascade of views on every page like this:
Sponsor View: .sponsor_html
Partner View: .partner_html
Default View: .html
The answer by Joe, of just removing .html works (really well) if you only have one level above the default, but in actual application I needed 5 levels in some cases.
There did not seem to be anyway to implement this short of some monkey patching in the same vein as Jeremy.
The Rails core makes some fairly wide ranging assumptions that you only want one format and that it maps to a single extension (with the default of NO extension).
I needed a single solution that would work for all view elements -- layouts, templates, and partials.
Attempting to make this more along the lines of convention I came up with the following.
# app/config/initializers/resolver.rb
module ActionView
class Base
cattr_accessor :extension_fallbacks
##extension_fallbacks = nil
end
class PathResolver < Resolver
private
def find_templates_with_fallbacks(name, prefix, partial, details)
fallbacks = Rails.application.config.action_view.extension_fallbacks
format = details[:formats].first
unless fallbacks && fallbacks[format]
return find_templates_without_fallbacks(name, prefix, partial, details)
end
deets = details.dup
deets[:formats] = fallbacks[format]
path = build_path(name, prefix, partial, deets)
query(path, EXTENSION_ORDER.map {|ext| deets[ext] }, details[:formats])
end
alias_method_chain :find_templates, :fallbacks
end
end
# config/application.rb
config.after_initialize do
config.action_view.extension_fallbacks = {
html: [:sponsor_html, :partner_html, :html],
mobile: [:sponsor_mobile, :partner_mobile, :sponsor_html, :partner_html, :html]
}
# config/initializers/mime_types.rb
register_alias 'text/html', :mobile
# app/controllers/examples_controller.rb
class ExamplesController
respond_to :html, :mobile
def index
#examples = Examples.all
respond_with(#examples)
end
end
Note: I did see the comments around alias_method_chain, and initially did make a call to super at the appropriate spot. This actually called ActionView::Resolver#find_templates (which raises a NotImplemented exception) rather than the ActionView::PathResolver#find_templates in some cases. I wasn't patient enough to track down why. I suspect its because of being a private method.
Plus, Rails, at this time, does not report alias_method_chain as deprecated. Just that post does.
I do not like this answer as it involves some very brittle implementation around that find_templates call. In particular the assumption that you only have ONE format, but this is an assumption made all over the place in the template request.
After 4 days of trying to solve this and combing through the whole of the template request stack its the best I can come up with.
The way that I'm handling this is to simply skip_before_filter on those requests that I know I want to render the HTML views for. Obviously, that will work with partials.
If your site has a lot of mobile and/or tablet views, you probably want to set your filter in ApplicationController and skip them in subclasses, but if only a few actions have mobile specific views, you should only call the before filter on those actions/controllers you want.
If your OS has symlinks you could use those.
$ ln -s show.html.erb show.mobile.erb
I am adding another answer now that we have updated to 3.2.X. Leaving the old answer as it was in case someone needs that one. But, I will edit it to direct people to this one for current versions.
The significant difference here is to make use of the "new" (since 3.1) availability of adding in custom path resolvers. Which does make the code shorter, as Jeroen suggested. But taken a little bit further. In particular the #find_templates is no longer private and it is expected that you will write a custom one.
# lib/fallback_resolver.rb
class FallbackResolver < ::ActionView::FileSystemResolver
def initialize(path, fallbacks = nil)
#fallback_list = fallbacks
super(path)
end
def find_templates(name, prefix, partial, details)
format = details[:formats].first
return super unless #fallback_list && #fallback_list[format]
formats = Array.wrap(#fallback_list[format])
details_copy = details.dup
details_copy[:formats] = formats
path = Path.build(name, prefix, partial)
query(path, details_copy, formats)
end
end
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
append_view_path 'app/views', {
mobile: [:sponsor_mobile, :mobile, :sponsor_html, :html],
html: [:sponsor_html, :html]
}
respond_to :html, :mobile
# config/initializers/mime_types.rb
register_alias 'text/html', :mobile
Here's a simpler solution:
class ApplicationController
...
def formats=(values)
values << :html if values == [:mobile]
super(values)
end
...
end
It turns out Rails (3.2.11) adds an :html fallback for requests with the :js format. Here's how it works:
ActionController::Rendering#process_action assigns the formats array from the request (see action_controller/metal/rendering.rb)
ActionView::LookupContext#formats= gets called with the result
Here's ActionView::LookupContext#formats=,
# Override formats= to expand ["*/*"] values and automatically
# add :html as fallback to :js.
def formats=(values)
if values
values.concat(default_formats) if values.delete "*/*"
values << :html if values == [:js]
end
super(values)
end
This solution is gross but I don't know a better way to get Rails to interpret a request MIME type of "mobile" as formatters [:mobile, :html] - and Rails already does it this way.
Yes, I'm pretty sure this is the right way to do this in rails. I've defined iphone formats this way before. That's a good question about getting the format to default back to :html if a template for iphone doesn't exist. It sounds simple enough, but I think you'll have to add in a monkeypath to either rescue the missing template error, or to check if the template exists before rendering. Take a look a the type of patches shown in this question. Something like this would probably do the trick (writing this code in my browser, so more pseudo code) but throw this in an initializer
# config/initializers/default_html_view.rb
module ActionView
class PathSet
def find_template_with_exception_handling(original_template_path, format = nil, html_fallback = true)
begin
find_template_without_exception_handling(original_template_path, format, html_fallback)
rescue ActionView::MissingTemplate => e
# Template wasn't found
template_path = original_template_path.sub(/^\//, '')
# Check to see if the html version exists
if template = load_path["#{template_path}.#{I18n.locale}.html"]
# Return html version
return template
else
# The html format doesn't exist either
raise e
end
end
end
alias_method_chain :find_template, :exception_handling
end
end
Here is another example of how to do it, inspired by Simon's code, but a bit shorter and a bit less hacky:
# application_controller.rb
class ApplicationController < ActionController::Base
# ...
# When the format is iphone have it also fallback on :html
append_view_path ExtensionFallbackResolver.new("app/views", :iphone => :html)
# ...
end
and somewhere in an autoload_path or explicitly required:
# extension_fallback_resolver.rb
class ExtensionFallbackResolver < ActionView::FileSystemResolver
attr_reader :format_fallbacks
# In controller do append_view_path ExtensionFallbackResolver.new("app/views", :iphone => :html)
def initialize(path, format_fallbacks = {})
super(path)
#format_fallbacks = format_fallbacks
end
private
def find_templates(name, prefix, partial, details)
fallback_details = details.dup
fallback_details[:formats] = Array(format_fallbacks[details[:formats].first])
path = build_path(name, prefix, partial, details)
query(path, EXTENSION_ORDER.map { |ext| fallback_details[ext] }, details[:formats])
end
end
The above is still a hack because it is using a private API, but possibly less fragile as Simon's original proposal.
Note that you need to take care of the layout seperately. You will need to implement a method that chooses the layout based on the user agent or something similar. The will only take care of the fallback for the normal templates.
Rails 4.1 includes Variants, this is a great feature that allow you to set different views for the same mime. You can now simply add a before_action and let the variant to do the magic:
before_action :detect_device_variant
def detect_device_variant
case request.user_agent
when /iPad/i
request.variant = :tablet
when /iPhone/i
request.variant = :phone
end
end
Then, in your action:
respond_to do |format|
format.json
format.html # /app/views/the_controller/the_action.html.erb
format.html.phone # /app/views/the_controller/the_action.html+phone.erb
format.html.tablet do
#some_tablet_specific_variable = "foo"
end
end
More info here.
You can in this case for the format to html. By example you want always use the html in user show method
class UserController
def show
..your_code..
render :show, :format => :html
end
end
In this case, if you request show on User controller you render all the time the html version.
If you want render JSON too by example you can made some test about your type like :
class UserController
def show
..your_code..
if [:mobile, :tablet, :html].include?(request.format)
render :show, :format => :html
else
respond_with(#user)
end
end
end
I made a monkey patch for that, but now, I use a better solution :
In application_controller.rb :
layout :which_layout
def which_layout
mobile? ? 'mobile' : 'application'
end
With the mobile? method you can write.
So I have a different layout but all the same views, and in the mobile.html.erb layout, I use a different CSS file.
I need the same thing. I researched this including this stack overflow question (and the other similar one) as well as followed the rails thread (as mentioned in this question) at https://github.com/rails/rails/issues/3855 and followed its threads/gists/gems.
Heres what I ended up doing that works with Rails 3.1 and engines. This solution allows you to place the *.mobile.haml (or *.mobile.erb etc.) in the same location as your other view files with no need for 2 hierarchies (one for regular and one for mobile).
Engine and preparation Code
in my 'base' engine I added this in config/initializers/resolvers.rb:
module Resolvers
# this resolver graciously shared by jdelStrother at
# https://github.com/rails/rails/issues/3855#issuecomment-5028260
class MobileFallbackResolver < ::ActionView::FileSystemResolver
def find_templates(name, prefix, partial, details)
if details[:formats] == [:mobile]
# Add a fallback for html, for the case where, eg, 'index.html.haml' exists, but not 'index.mobile.haml'
details = details.dup
details[:formats] = [:mobile, :html]
end
super
end
end
end
ActiveSupport.on_load(:action_controller) do
tmp_view_paths = view_paths.dup # avoid endless loop as append_view_path modifies view_paths
tmp_view_paths.each do |path|
append_view_path(Resolvers::MobileFallbackResolver.new(path.to_s))
end
end
Then, in my 'base' engine's application controller I added a mobile? method:
def mobile?
request.user_agent && request.user_agent.downcase =~ /mobile|iphone|webos|android|blackberry|midp|cldc/ && request.user_agent.downcase !~ /ipad/
end
And also this before_filter:
before_filter :set_layout
def set_layout
request.format = :mobile if mobile?
end
Finally, I added this to the config/initializers/mime_types.rb:
Mime::Type.register_alias "text/html", :mobile
Usage
Now I can have (at my application level, or in an engine):
app/views/layouts/application.mobile.haml
and in any view a .mobile.haml instead of a .html.haml file.
I can even use a specific mobile layout if I set it in any controller:
layout 'mobile'
which will use app/views/layouts/mobile.html.haml (or even mobile.mobile.haml).
I solved this problem by using this before_filter in my ApplicationController:
def set_mobile_format
request.formats.unshift(Mime::MOBILE) if mobile_client?
end
This puts the mobile format to the front of the list of acceptable formats. So, the Resolver prefers .mobile.erb templates, but will fall back to .html.erb if no mobile version is found.
Of course, for this to work you need to implement some kind of #mobile_client? function and put Mime::Type.register_alias "text/html", :mobile into your config/initializers/mime_types.rb
I would like to be able to map URLs to Controllers dynamically based on information in my database.
I'm looking to do something functionally equivalent to this (assuming a View model):
map.route '/:view_name',
:controller => lambda { View.find_by_name(params[:view_name]).controller }
Others have suggested dynamically rebuilding the routes, but this won't work for me as there may be thousands of Views that map to the same Controller
This question is old, but I found it interesting. A fully working solution can be created in Rails 3 using router's capability to route to a Rack endpoint.
Create the following Rack class:
class MyRouter
def call(env)
# Matched from routes, you can access all matched parameters
view_name= env['action_dispatch.request.path_parameters'][:view_name]
# Compute these the way you like, possibly using view_name
controller= 'post'
my_action= 'show'
controller_class= (controller + '_controller').camelize.constantize
controller_class.action(my_action.to_sym).call(env)
end
end
In Routes
match '/:view_name', :to => MyRouter.new, :via => :get
Hint picked up from http://guides.rubyonrails.org/routing.html#routing-to-rack-applications which says "For the curious, 'posts#index' actually expands out to PostsController.action(:index), which returns a valid Rack application."
A variant tested in Rails 3.2.13.
So I think that you are asking that if you have a Views table and a View model for it where the table looks like
id | name | model
===================
1 | aaa | Post
2 | bbb | Post
3 | ccc | Comment
You want a url of /aaa to point to Post.controller - is this right?
If not then what you suggest seems fine assuming it works.
You could send it to a catch all action and have the action look at the url, run the find_by_name and then call the correct controller from there.
def catch_all
View.find_by_name('aaa').controller.action
end
Update
You can use redirect_to and even send the params. In the example below you I am sending the search parameters
def catch_all
new_controller = View.find_by_name('aaa').controller
redirect_to :controller => new_controller, :action => :index,
:search => params[:search]
end
Here is a nice Rack Routing solution to SEO contributed by zetetic and Steve ross
Testing Rack Routing Using rSpec
It shows you how to write a custom dispatcher (where you can do a db lookup if needed) and with constraints, and testing as well.
As suggested in the question Rails routing to handle multiple domains on single application, I guess you could use Rails Routing - Advanced Constraints to build what you need.
If you have a limited space of controllers (with unlimited views pointing to them), this should work. Just create a constraint for each controller that verifies if the current view matches them.
Assuming you have a space of 2 controllers (PostController and CommentController), you could add the following to your routes.rb:
match "*path" => "post#show", :constraints => PostConstraint.new
match "*path" => "comment#show", :constraints => CommentConstraint.new
Then, create lib/post_constraint.rb:
class PostConstraint
def matches?(request)
'post' == Rails.cache.fetch("/view_controller_map/#{request.params[:view_name]}") { View.find_by_name(request.params[:view_name]).controller }
end
end
Finally, create lib/comment_constraint.rb:
class CommentConstraint
def matches?(request)
'comment' == Rails.cache.fetch("/view_controller_map/#{request.params[:view_name]}") { View.find_by_name(request.params[:view_name]).controller }
end
end
You can do some improvements, like defining a super constraint class that fetches the cache, so you don't have to repeat code and don't risk fetching a wrong cache key name in one of the constraints.