gistfile1.txt

import Foundation

class QueryResult {} // if I make this class public then the compiler says that generate has to be declared public.
                     // If I make generate public I get a different error... 
                     // But QueryResult is a class which has to be public... it is part of my public API...
public class Row {}

class QueryResultGenerator : GeneratorType {
  typealias Element = Row
  func next() -> Element? {
    return nil
  }
}

extension QueryResult : SequenceType {
  typealias GeneratorType = QueryResultGenerator
  
  func generate() -> GeneratorType {
    return QueryResultGenerator()
  }

}

I think that if you have a public class, the public methods must return only types that are public. As the class is public, it can be called from external code, that need to have access to all the types involved. It is your intention to create a public class or a private class?

Making all things public does compile and It should be correct by a logical point of view. If you want to keep QueryResultGenerator private I think you'll need to create some wrapper class.

import Foundation

public class QueryResult {}
public class Row {}

public class QueryResultGenerator : GeneratorType {
    public typealias Element = Row
    public func next() -> Element? {
        return nil
    }
}

extension QueryResult : SequenceType {
    public typealias GeneratorType = QueryResultGenerator

    public func generate() -> GeneratorType {
        return QueryResultGenerator()
    }

}

Thanks man!

Your code works.

To answer your question:

I would like QueryResult to be a public class and I would like to be able to use it in a for loop like this:

let r = QueryResult(...)
for row in r {
    r.doSomething()
}

I am only able to do this if I make the generator public. You mentioned that:

If you want to keep QueryResultGenerator private I think you'll need to create some wrapper class.

QueryResultGenerator does not have to be private so all is good. Thanks!