![]() It combines the elements of its upstream publishers, respecting the order in which the elements are emitted. This makes sense if you understand how the zip operator works. What is unique about the zip operator is that it publishes its first element when every upstream publisher published an element. As I explained earlier, the Output type of the publisher is a tuple composed of the elements of the upstream publishers, (Int, String) in this example. The zip operator creates a publisher that republishes the elements of its upstream publishers. If the first subject emits a third element, nothing happens. The first element the zip publisher publishes is a tuple consisting of the first element of the first subject and the first element of the second subject. The zip publisher emits its first element the moment the second subject emits an element. Even when the first subject emits a second element, the zip publisher still doesn't emit an element. In other words, the zip publisher doesn't emit an element. Notice that nothing is printed to the console. ![]() The first subject starts by emitting an integer. Let's take a look at the elements the zip publisher emits when the upstream publishers start emitting elements. In this example, the Output type of the zip publisher is a tuple of type (Int, String). The value of the element the publisher emits is a tuple, combining the values of the elements of the upstream publishers. In the value handler, we print the value of the element the publisher emits. In the completion handler, we use a switch statement to switch on the Completion object. We invoke the sink(receiveCompletion:receiveValue:) method on the resulting publisher. Publishers.Zip(intSubject, stringSubject) It is up to you to decide which option you prefer. The initializer of the Zip struct accepts the publishers you want to combine as arguments. It is also possible to combine publishers using the Publishers.Zip struct. We combine the subjects by applying the zip operator to the first subject, passing in the second subject. The second subject emits elements of type String. The first subject emits elements of type Int. Combining Publishers with Combine's Zip Operatorįire up Xcode and create a playground by choosing the Blank template from the iOS section.Ĭlear the contents of the playground and add an import statement for the Combine framework. In this episode, I show you how to use the zip operator to combine publishers. Each of these operators serves a specific purpose. The Combine framework defines a number of operators to combine two or more publishers into a single publisher.
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