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Editorial Team
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Asked: 2026-05-15T00:25:58+00:00

In my Rails app I have a fairly standard has_many relationship between two entities.

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In my Rails app I have a fairly standard has_many relationship between two entities. A Foo has zero or more Bars; a Bar belongs to exactly one Foo. Both Foo and Bar are identified by a single integer ID value. These values are unique across all of their respective instances.

Bar is existence dependent on Foo: it makes no sense to have a Bar without a Foo.

There’s two ways to RESTfully references instances of these classes. Given a Foo.id of “100” and a Bar.id of “200”:

  1. Reference each Foo and Bar through their own “top-level” URL routes, like so:

    • /foo/100
    • /bar/200

  2. Reference Bar as a nested resource through its instance of Foo:

    • /foo/100
    • /foo/100/bar/200

I like the nested routes in #2 as it more closely represents the actual dependency relationship between the entities. However, it does seem to involve a lot of extra work for very little gain. Assuming that I know about a particular Bar, I don’t need to be told about a particular Foo; I can derive that from the Bar itself. In fact, I probably should be validating the routed Foo everywhere I go (so that you couldn’t do /foo/150/bar/200, assuming Bar 200 is not assigned to Foo 150). Ultimately, I don’t see what this brings me.

So, are there any other arguments for or against these two routing schemes?

Point of Clarification

I’m concerned mostly about RESTful updates/shows/deletes to particular Bars. For getting a list of Bars for a specific Foo (which is usually the “index” action in Rails) it makes perfect sense to have a nested route such as /foo/100/bar. The page at this route could just as easily link to /bar/x as /foo/100/bar/x though.

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1 Answer

  1. Editorial Team

    You’re looking for shallow routes. As you pointed out, the idea of having a deeply nested route for things like creates, updates is unnecessary since you are targeting the desired record directly.

    I have never actually done the shallow routing thing so I’ll pass on the railscast episode where Ryan Bates explains it probably better than I could: 139 Nested Resources.

    Edit: You can read up a little more on the guides for routing 3.8.4.

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