ReactiveKit | A Swift Reactive Programming Kit

ReactiveKit is a Swift library. ReactiveKit has no bugs, it has no vulnerabilities, it has a Permissive License and it has medium support. You can download it from GitHub.

Consider how text of a text field changes as user enters his name. Each entered letter gives us a new state. We can think of these state changes as a sequence of events. It is quite similar to an array or a lists, but with the difference that events are generated over time as opposed to having them all in memory at once. The idea behind reactive programming is that everything can be represented as a sequence. Let us consider another example - a network request. Outcome of a network request is a response. Although we have only one response, we can still think of it as a sequence. An array of one element is still an array. Arrays are finite so they have a property that we call size. It is a measure of how much memory the array occupies. When we talk about sequences over time, we do not know how many events will they generate during their lifetime. We do not know how many letters will the user enter. However, we would still like to know when the sequence is done generating the events. To get that information, we can introduce a special kind of event - a completion event. It is an event that marks the end of a sequence. No event shall follow the completion event. We will denote completion event visually with a vertical bar. Completion event is important because it tells us that whatever was going on is now over. We can finalize the work at that point and dispose any resources that might have been used in processing the sequence. Unfortunately, the universe is not governed by the order, rather by the chaos. Unexpected things happen and we have to anticipate that. For example, a network request can fail so instead of a response, we can receive an error. In order to represent errors in our sequences, we will introduce yet another kind of event. We will call it a failure event. Failure event will be generated when something unexpected happens. Just like the completion event, failure event will also represent the end of a sequence. No event shall follow the failure event. Let us see how the event is defined in ReactiveKit. It is just an enumeration of the three kinds of events we have. Sequences will usually have zero or more .next events followed by either a .completed or a .failed event. What about sequences? In ReactiveKit they are called signals. Here is the protocol that defines them. A signal represents the sequence of events. The most important thing you can do on the sequence is observe the events it generates. Events are received by the observer. An observer is nothing more than a function that accepts an event.