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()
  }

}

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!