This is an experimental repository for Sourcery stencil template for generating listener managers.
Let's say you have a Service class. This Service issues different events during its lifetime.
The list of events can be expressed as a protocol or an enum.
In this repo I wanted to explore the protocol option.
The events list protocol: ServiceEventListener
protocol ServiceEventListener: class {
func connectionStateChanged(_ state: ServiceConnectionState)
func serviceEvent1(event1: ServiceEvent1)
func serviceEvent2(event2: ServiceEvent2, additionalContext: ServiceContext)
func serviceReset()
}Our Service should support multiple listeners, so we need to keep an array of listeners.
When an event occurs, we run through the list of listeners and invoke a corresponding method.
If we have lots of events and services - we will have to write a lot boilerplate code.
In Objective-C we could implement it via delegate proxies (refer to this article for more details: Smart Proxy Delegation).
In Swift we can generate all the boilerplate using Sourcery.
This stencil template generates the following code (container is a helper class that manages the list of listeners)
class ServiceEventListenerManager: ServiceEventListener {
private let container: ListenerContainer<ServiceEventListener> = ListenerContainer()
func addListener(_ listener: ServiceEventListener) {
container.addListener(listener)
}
func removeListener(_ listener: ServiceEventListener) {
container.removeListener(listener)
}
func connectionStateChanged(_ state: ServiceConnectionState) {
container.forEach { listener in
listener.connectionStateChanged(state)
}
}
func serviceEvent1(event1: ServiceEvent1) {
container.forEach { listener in
listener.serviceEvent1(event1: event1)
}
}
func serviceEvent2(event2: ServiceEvent2, additionalContext: ServiceContext) {
container.forEach { listener in
listener.serviceEvent2(event2: event2, additionalContext: additionalContext)
}
}
func serviceReset() {
container.forEach { listener in
listener.serviceReset()
}
}
}