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fastdude7's avatar
New Contributor
5 years ago

Specifying types which are subset of String

Hi, I would like to specify an API which returns a FooId. A FooId is a 4 character String consisting of ascii alphanum chars.

When I end up generating my API I make it so that the FooId is not a wrapper for a string instead I just return:

    fooId: "abcd",
someThingElse: "a",
number: 2

Is it possible to specify in the swagger doc (openAPI) that:

  • A FooId should be treated like a string, no wrapping class for example.
  • While preserving the fact that it is a FooId so a client consuming the swagger doc knows which APIs really return strings and which ones are returning a FooId, so no information is lost.

Does the spec support this?


full disclosure I asked a similar question on stack overflow which got no responses


3 Replies

    • fastdude7's avatar
      New Contributor

      So I assume:

            type: string
            pattern: '^\d{3}-\d{2}-\d{4}$'

      this is defining something like what I want, where the type is 'ssn' but it is really just a string.

      If I was to have a list of `ssn` could it look like:


      ie no wrapping class.
      So should this mean that something like:

      "schema": {
          "type": "array",
          "items": {
              "$ref": "#/definitions/FooId"

      and in definitions

      "FooId": {
          "type": "string",
          "title": "FooId"

      would work to define an array of FooId where FooId is really just a string type. When the API responds that looks like:

      ["abcd", "abcd"]

      If this is the case then it looks like at least the standard supports. So now I need to find out why springfox is not making those types.

      Was this supported in version 2?

      • fastdude7's avatar
        New Contributor

        Hi so in the end what I am doing is generating types in the definitions section like so:

        FooId : {
             "type": "string",
             "title": "CollectionId"

        the swagger API UI seems to be happy with that, and I assume that is legit.