gistfile1.txt

import Foundation

class ConsumerOperation<T> : Operation {
    private var consumer: (T) -> Void
    private weak var prodcuer: ProducerOperation<T>?
    
    init(prodcuer: ProducerOperation<T>, consumer: (T) -> Void) {
        self.prodcuer = prodcuer
        self.consumer = consumer
        super.init()
    }
    
    override func main() {
        if let res = prodcuer?.result {
            consumer(res)
        }
    }
}

class ProducerOperation<T> : Operation {
    var result: T?
    var producer: () -> T
    init(producer: () -> T) {
        self.producer = producer
        super.init()
    }
    
    override func main() {
        result = producer()
    }
}