[Swift] Inheritance issue

[SergeyPetrachkov]

Description

Hi guys, I've installed the latest generator via homebrew and now I'm trying to generate a client for my iOS app.
I appreciate structs over classes (Apple does too!), but here is one problem with inheritance, as Swift structs being value types do not support inheritance. There's a base class and a few descendants described in API yaml. Descendants do not inherit base's properties and I get invalid API client.

openapi-generator version

3.3.4 (latest available with Homebrew

OpenAPI declaration file content or url

here is a gist

Sorry, I can't provide the full spec

Command line used for generation

openapi-generator generate -l swift4 -i XXX

Suggest a fix/enhancement

I would think of either generating abstract descendants as classes or use a composition pattern and stay with structs. Though I am not sure either is easily possible

[auto-labeler]

👍 Thanks for opening this issue!
🏷 I have applied any labels matching special text in your issue.

The team will review the labels and make any necessary changes.

[wing328]

cc @jgavris (2017/07) @ehyche (2017/08) @Edubits (2017/09) @jaz-ah (2017/09) @d-date (2018/03)

[wing328]

What about using protocol as suggested in https://stackoverflow.com/a/48820067/677735 ?

[d-date]

Please make more clear your problem. I think it makes more complex your code. Inheritance is too much complex to generate code and as you know struct is prefer than class.

You may think protocol is one of the solution to introduce inheritance to struct, but not equal to inheritance. Please check protocol oriented programming in Swift.

[SergeyPetrachkov]

Take a look at the attached gist. I know how to make things work and what is the POP though autogenerated code is supposed to be automatically generated and work out of the box.

On Sat, 6 Apr 2019 at 15:29, Daiki Matsudate ***@***.***> wrote: Please make more clear your problem. I think it makes more complex your code. Inheritance is too much complex to generate code and as you know struct is prefer than class. You may think protocol is one of the solution to introduce inheritance to struct, but not equal to inheritance. Please check protocol oriented programming in Swift. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#2588 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHoB-LYkdZrhQBZ3B7y8T04ETpzcse4pks5veFrWgaJpZM4ccBGv> .

-- Sent from Gmail Mobile

[d-date]

I understand your point.
To be true, nobady implement to allOf, anyOf and oneOf.
It makes big breaking changes in Swift. And if you have something make sense, we’re welcome to your PR.

[SergeyPetrachkov]

Hi guys,

I've been thinking about polymorphism thing and faced this problem on one of projects im working on.

protocol DashboardDataContext: Codable {
  var type: DashboardItemType { get }
  func toDashboardViewModel() -> ASCollectionModel
}

struct AnyDashboardDataContext {
   var context: DashboardDataContext
}

enum DashboardItemType: String, Codable {
  case ad, panel, collection
  
  var metaType: DashboardDataContext.Type {
    switch self {
    case .ad:
      return AdvertisementCluster.self
    case .panel:
      return NavigationPanelContext.self
    case .collection:
      return InfoClusterContext.self
    }
  }
}

extension AnyDashboardDataContext: Codable {
  private enum CodingKeys: CodingKey {
    case type, context
  }
  
  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let type = try container.decode(DashboardItemType.self, forKey: .type)
    self.context = try type.metaType.init(from: container.superDecoder(forKey: .context))
  }
  
  func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(context.type, forKey: .type)
    try context.encode(to: container.superEncoder(forKey: .context))
  }
}

So here is a workaround, and I believe it's possible to get this approach to work on a template level.

So if we have a method that can return an array of different objects that are inherited from one base model we need:

• create enum based on discriminator
• create protocol XXXModel with a property of discriminator enumeration
• create wrapper protocol around XXXModel which will contain XXXModel property as a context, say AnyXXXModel
• implement Codable for AnyXXXModel like above

when deserializing:

let newChain = try JSONDecoder().decode([AnyDashboardDataContext].self, from: jsonData)
return newChain.compactMap({ $0.context })

when serializing:

let wrappedChain: [AnyDashboardDataContext] = sections.map({ AnyDashboardDataContext(context: $0) })
let jsonData = try JSONEncoder().encode(wrappedChain)
let jsonString = String(data: jsonData, encoding: .utf8)

[SergeyPetrachkov]

Hi @d-date, i've checked c# client. it seems to work through anyOf, oneOf. I am not sure how it does it, but it does.

[pupubird]

Having class to be inheritable makes it much more flexible and usable in cases that we wanted to compose multiple models together

[wing328]

@pupubird would you have time to contribute a PR? I can work with you on that.

[iDevPro]

2025 year ;) Anyone try to find solution
I start patch Template, it work normally but I have one property from parent class, which break my heart :(

My fixed template here
modelObject.mustache.txt

Need to skip item from allVars list where baseName == parentModel.discriminator.propertyName but mustache is not for calculation inside pattern :)

Also I found information about Swift5+ generators break inheritance at all :(
The POP is not solution when you need equal behaviour like in Kotlin language