Firstly, we created some publishers

let publisher = Publishers.Just("Combine Swift")
let sequencePublisher = let publisher = Publishers.Sequence(sequence: [1,2,3,5,6])

Call sink to subscribe to a publisher

let publisher = Publishers.Just("Combine Swift")
let subscribtion = publisher.sink { value in
  print(value)
}

cancel the subscription

subscriber.cancel()

Subjects

let subject = PassthroughSubject<String, Never>()
let publisher = subject.eraseToAnyPublisher()

let subscriber = publisher.sink(receiveValue: { value in
    print(value)
})

subject.send("Combine") //The Subscriber will print "Combine"
subject.send("Swift")   //The Subscriber will print "Swift"

A subject can have multiple subscribers

let subject = PassthroughSubject<String, Never>()
let publisher = subject.eraseToAnyPublisher()


let subscriber1 = publisher.sink(receiveValue: { value in
    print(value)
})

//subscriber1 will recive the events but not the subscriber2
subject.send("Event1")
subject.send("Event2")


let subscriber2 = publisher.sink(receiveValue: { value in
    print(value)
})
//Subscriber1 and Subscriber2 will recive this event
subject.send("Event3")