Rails: link_to / form_for doesn't work for singular resource

[Godisemo]

In my routes I have

resource :company

and in my views

<% form_for(@store) do |f| %>
    …
<% end %>

When

new action gets an error when rendering

undefined methodhash_for_companies_path' for #`

The stack trace reviels that the problem occurs in

lib/action_dispatch/routing/polymorphic_routes.rb:133:inpolymorphic_url'`

edit action can render without errors but the forms url is /company.4 where 4 is the id of the company.

This seems to be a bug that has been around for a very long time so I think it's time to fix it.

[pixeltrix]

You're right the error has been around for a long while however a clean solution doesn't readily represent itself. The polymorphic_url helper has no 'intelligence' in how it operates - it has no information about what you've declared as resources in your routes.rb. All it has to go on it the name of the model and how that maps to the named url helpers.

In your case when passing a new Company instance it tries to map to the plural path as that's the standard route for the create action. The question is how to determine a singular resource from a regular resource - suggestions are welcome. The best solution I can think of is to try a respond_to? first and if it doesn't then try the singular option - I'll take a look at it.

[gucki]

Ah, didn't know there's already a ticket for htis. So here's my post from the mailing list:

What about making the polymorphic routing in rails to try a plural route first. If it fails, try a singleton route. If it fails, raise.

This is not the nicest and most performant way (the result could be cached in production so it doesn't really matter in the end) but I guess it should solve most cases. Or is this too much magic?

[wildchild]

I am wondering why this ticket pointed to 3.2 milestone?

[pixeltrix]

Because it’s not a blocker for the 3.1 release and it may require too many changes to go into a patch release.

[mikeni]

i think this bug should be written in rails guides somewhere.

for anyone using a singular resource, they will eventually find themselves on this bug page. better to announce first

[maximeg]

Still occurring.

[mikeni]

for now i just use scope =(

[phantomwhale]

Yep, my first time with the singular resource form, and I walked smack into this bug. Would be great to see a fix in an upcoming version - don't see any target milestone, so I presume it's not under active development at the moment ?

[kjakub]

Yep, here too, my first time with singular resource, lost 3h coz i was blaming myself like a first

[glebm]

+1

[felipero]

I believe respond_with has the same problem.

[pixeltrix]

@felipero yes it will - as will anything where you can pass a model instance and get a url.

I haven't forgotten about this issue, it's just trickier than it seems to fix. The problem is there is no easy way to discern whether a model maps to a singular or a regular resource url. Checking for the presence of a collection url doesn't work as the resource may have been specified with :except => :index and trying to rescue route generation errors doesn't work because passing an instance to a singular resource url helper will generate a url with the format set to the id and no exception.

The only apparent way I can think of doing it is by creating a data structure that keeps a track of whether a set of routes is a singular resource and then querying that data structure in polymorphic_url. However before I or someone else can go ahead with that there needs to be a discussion whether we want the overhead of that structure.

[felipero]

Well, it is a non-blocking issue. Thanks for you prompt answer. :)

[zelig]

I think someone ought to patch this. My thinking would not be along the lines of trying routes to fail (and fall back on the plural as in the comments in the rails issue) but go after association reflections.

Can we make the assumption that behind every nested resource form there is an activerecord association? No but we can test it

for form_for [a, b] (of classes A, B) if there is a model class A with has_many assoc to B, we can safely assume, expect that routes are set up to support a plural ("a_bs_path") for create. If there is a has_one we can safely assume, expect that routes are set up to support a singular ("a_bs_path"). If we find none, we fall back to the plural as the status quo educated guess. My 2 cents. Is this against modularity and decoupling MVC?

[pixeltrix]

@zelig firstly, I think anything like that is tying your models to your routes too much. Secondly, what about non-AR models, and finally it doesn't fix the problem for top-level singular resources, e.g;

class Basket < ActiveRecord::Base
end

resource :basket

There's nothing in the model that's going to help with that - the only way it to store the fact that it's a singular resource and query that when generating the url. Adding metadata to the model won't help as a model may sometimes be a singular resource (/account) or a multiple resource (/admin/users/1).

[zelig]

Surely this doesn't solve all problems but in the special case of nested AR resources, plurality can be reasonably guessed using model class associations, for others (i.e., top-level resource or non-AR models or models with implicit associations) the plural is a decent guess. This sounds to me a simple improvement but maybe the caveat is that it is not the right solution.

So where would you store resource singularity so that polyorphic_url could access this info? In case people are interested in fixing this ugly duckling.

[jakevose]

Add me to the list of people who just lost a bunch of time trying to figure out the "right" way to work around this and thinking myself crazy before stumbling upon this obscure reference to a long-standing, known bug.

[pjg]

Add me to the list of people who just lost a bunch of time trying to figure out the "right" way to work around this and thinking myself crazy before stumbling upon this obscure reference to a long-standing, known bug.

And me as well.

[pjg]

To anyone stumbling upon this issue, the workaround is quite simple. Given:

resource :billing_info

You generate the form_for call like this:

= form_for @billing_info, url: billing_info_path do |f|

[gmile]

@pjg one of the nice features of form_for is to generate a proper url, based on object's persistance state, i.e. autodetect a path with either _create or _update affixes. That said, i'm unsure if the solution you propose will handle both cases at the same time. Will it?

[pjg]

Yeah, it does handle both :create and :update actions.

[asymmetric]

It would be really nice to have this fixed, or at least to have the problem prominently documented somehow. Just spent 2hrs thinking it was an error on my end!

[jlbenc]

Wasted 2+ hours hunting this issue down, :(

Thanks @pjg for your workaround! :+1:

[gaurish]

Today, I faced issue too. solved via workaround given Thanks @pjg :+1:

[hasghari]

I agree with @mikeni that this bug should be documented in the Rails guides.

[nazar]

Thanks @pijg for saving me an hour or three

[gustavokloh]

+1 for this issue!

And one more thanks @pjg

[nl0pvm]

Wasted 1,5 hours hunting this issue down :-1:

[leebrooks0]

All in All using singular resources as a newbie is a huge PITA

[codyrobbins]

The above documentation fix should at least hopefully prevent anyone else from running into this bug until it’s fixed.

[jonleung]

I love how this is still a bug lol

[tute]

@rafaelfranca, can I help you squash this?

[rafaelfranca]

Of course. Pull requests are always welcome. Make sure to ping @pixeltrix if you got a fix

[tute]

@rafaelfranca got the failing test from @athal7 running on current master, but seems I'll need some help. The issue is ActionDispatch::Routing::PolymorphicRoutes#polymorphic_path not knowing if the route was defined as singular or not. See https://github.com/rails/rails/issues/1769#issuecomment-5506213. How to approach it?

[pixeltrix]

@tute you refactor the routing code, adding a :model option to resource and resources so that we can map from the model class to the route and the route needs to keep track of whether it's a singular or collection resource. That way you can directly lookup the correct route and not infer the route name from the model class.

That's how I plan to do if for Rails 4.1 :persevere:

[tute]

I'd love a way for PolymorphicRoutes to check the routes of the app. That way, and I know it's obvious, from the record it could check if it relates to a singular ot collection resource.

Too many moving parts for my new-to-rails-code brain. Would love to peek onto your machine while you work if that's fine with you, so I learn and can help in upcoming ones!

[stephdatu]

Can't wait til this is fixed! Thanks, yet again, @pjg

[mikepence]

+1

[rosswilson]

I too have just encountered this issue, it'd be great if a fix can be found

[RKushnir]

How about having a singular option? What do you think?

form_for @resource, singular: true

I guess, this would then have to be passed down to polymorphic_url.

[pixeltrix]

@RKushnir there's already a :url option so that doesn't really buy us anything since the create url and update url are the same, e.g:

form_for @resource, url: resource_url

I promise to fix it for 4.1 :smile:

[RKushnir]

@pixeltrix I can't totally agree. True that it doesn't buy anything in terms that we still have to pass an option, yet there's some profit in it. It's easier to type and abstract the singular option(or even make a helper singular_form_for) to use in all cases, instead of providing specific url option for each case individually.

Do you already have any ideas on how you would fix it?
An easier way would be to allow users to override some method in the model(i.e. model_name.route_key) to specify a singular form, but it's a view+routes issue and involving the model would be highly undesirable.
Another option would be to make polymorphic_url dependent on the router, so it has enough information about the resource, but seems like it would add much logic into polymorphic_url.

[codyrobbins]

@RKushnir: I’m with @pixeltrix that adding a singular option doesn’t really gain you anything when you can already use the url option to work around the problem. Adding an additional special-purpose option when there’s already a workaround is just cruft as opposed to fixing the underlying behavior.

[RKushnir]

@codyrobbins Yeah, agree it's a cruft. But in a situation when workaround has become the standard because the bug stays unresolved for years, the hope is almost gone :frowning: I doubt if there's a clean way for

fixing the underlying behavior

Leaving the form_for options aside, if we had a concrete idea on how it should be done, it would increase the chance that someone makes a so long-awaited pull request. So, ideas?

[pixeltrix]

@RKushnir you fix it in the router by linking the model class directly to the route rather than guessing the url helper name based on the model class, e.g.

# default :model option of Post
resources :posts

# default :model option of Basket - router knows that it's a singular resource route
resource :basket

# custom :model option - form_for @user uses singular resource route account_url
resource :account, model: 'User'

This needs significant refactoring of Journey, Mapper, RouteSet, etc. classes - I'm not expecting a PR to appear like magic so I'll be doing it myself. I had hoped to get it done for 4.0 but illness restricted the amount of time I had available.

There are some kinks to work out like what happens when a resource is used in a singular and normal context (e.g. /account for current user and /users/1 for user pages). Also there's the issue of how to handle namespaces routes like admin - currently you use an array like [:admin, @user] so I'd like to be able to continue using that.

[RKushnir]

what happens when a resource is used in a singular and normal context

That's one of the reasons why you shouldn't let the model mess with this.

[vlad-shatskyi]

In case anybody is looking for a workaround:

class Company < ActiveRecord::Base
  model_name.instance_variable_set(:@route_key, 'company')
end

http://stackoverflow.com/a/16229154/1149074

[pixeltrix]

@shockone that only works if your model is accessed via the singular resource url only - if you have a resource that's accessed via both then you'll break the other one.

[Frankky]

I've spent my last two weeks trying to deal with this issue with any suggestion I found on the internet. I still have my question here: http://stackoverflow.com/questions/23994887/rails-one-to-one-relationship-and-form-for-sending-format-instead-of-id-and-par/23994996#23994996. I'm writing here today not only because I'm desperate to find a cure to this rails issue (the workarounds I found didn't work) or a git example with a working app using singular resource and form_for. But also to underline this problem with a nested singular resource like resources :users do resource :profile end. I just hope that the solution you'll find will handle this case too.

[hasghari]

@Frankky I have responded to your problem in stackoverflow.

[schlick]

I'd just like to add that the solution offered in https://github.com/rails/rails/issues/1769#issuecomment-9556381 isn't viable when dealing with a polymorphic nested singular resource since you need to use polymorphic_path directly in the url option as the parent resource can be one of many. The solution offered in https://github.com/rails/rails/issues/1769#issuecomment-41025758 worked well and meant I didn't even need to use the url option. But as has already been mentioned, this means you end up polluting your model class with a hack to make your views work and will break if your model is used by a collection route as well.

[stiff]

How about this approach: when route is defined (resource :account) lookup the corresponding model class (Account). If there is one mark it as singular (maybe for given prefixes? model may have different resources like namespace :admin do resources accounts; end; subdomain account_name do resource account end), if there is no, then this problem is very unlikely (only if it's crafted at runtime, or something like that).

[siax84]

Not sure if it can help to fix the overall problem but I helped myself the following way, since https://github.com/rails/rails/issues/1769#issuecomment-9556381 did not work properly for my new action

form_for(@equipment, :url=> {:action=> (@equipment.new_record? ? 'create' : 'update')}) do |f|

EDIT: slightly modified to make it work also when validation errors come up.

[simnalamburt]

Is there any workaround of this bug for the method respond_with? :sob:

[RKushnir]

@simnalamburt Try respond_with @thing, location: your_singular_thing_url(@thing).

[azul]

@pixeltrix, How about trying the plural route first. Then catching the undefined method error in polymorphic_url and trying the singular route?
That would not solve the problem when both methods are defined. But I think it would be easy to document and understand. If one has both a resource and resources defined for the same model they will have to state which one they want anyway (using the url option for example).

[justinplus]

The workaroud I use is to add as: to change the path helper for singular resource, like
resource company, as: :companies

[philipgiuliani]

Why a bug like this isn't fixed yet?

[notrab]

@philipgiuliani I'm sure you'll discover, judging by the comments above, there isn't any easy way to do this without polluting other classes within Rails for this behaviour.

The workaround is quite simple and to be honest, I don't see a problem. Throw it in the docs and just be done with it. Adding url: to the form declaration isn't so hard work for singular routes.

😴

[rails-bot]

This issue has been automatically marked as stale because it has not been commented on for at least
three months.

The resources of the Rails team are limited, and so we are asking for your help.

If you can still reproduce this error on the 4-2-stable, 4-1-stable branches or on master,
please reply with all of the information you have about it in order to keep the issue open.

Thank you for all your contributions.

[rafaelfranca]

See https://github.com/rails/rails/pull/17066#issuecomment-57363051

[schuetzm]

@rafaelfranca Care to explain why you closed this issue? The comment you referenced says it is still open "because it's a difficult problem to solve". Has it finally been fixed?

[rafaelfranca]

Oops! Looks like I linked to the wrong comment. I could not find the comment that I explained that it is fine to use the :url option and that this problem is not something that we need to fix.

https://github.com/rails/rails/pull/23138 may fix this issue introducing a new API.

[matkoniecz]

Why it is closed? #23138 is not merged and it is explicitly documented as existing bug in http://guides.rubyonrails.org/v4.1/routing.html

[azul]

@matkoniecz - it's documented as you said including a workaround with the url param. And there is a bug that may fix this in the longer run. I think that is why it's closed. #23138 will track the progress on the fix now.

[IamNaN]

For anyone landing here via google, this is what got implemented: http://edgeguides.rubyonrails.org/routing.html#singular-resources

In short, add something like resolve('User') { [:user] } after you define the singular resource in routes.rb, where 'User' is the class name and :user is the resource name.

[tomrossi7]

Couldn't this be fixed in the latest rails implementation by changing the behavior of form_with?