How do modules (plugins) work?
Would not be cool for those who may create objects that might work collectively with out realizing about one another? Think about that you’re constructing a dynamic kind. Based mostly on some inner situations, the fields are going to be composed utilizing the info coming from the enabled modules.
For instance you’ve gotten module A, B, C, the place A is offering you Discipline 1, 2, 3, the B module is caring for Discipline 4, 5 and C is the supplier of Discipline 6. Now for those who flip off B, it is best to solely be capable to see discipline 1, 2, 3 and 6. If all the things is turned on it is best to see all of the fields from 1 to six.
We are able to apply this very same sample to many issues. Simply take into consideration one of many largest plugin ecosystem. WordPress is utilizing hooks to increase the core functinalities by means of them. It is all based mostly on the idea I simply talked about above. That is a part of the event-driven structure design sample. Now the query is how can we implement one thing comparable utilizing Swift? 🤔
A hook system implementation
First we begin with a protocol with some extent of invocation. This methodology will probably be referred to as by the module supervisor to invoke the right hook operate by title. We’ll go round a dictionary of parameters, so our hooks can have arguments. We’re utilizing the Any sort right here as a worth, so you’ll be able to ship something as a parameter beneath a given key.
protocol Module {
func invoke(title: String, params: [String: Any]) -> Any?
}
extension Module {
func invoke(title: String, params: [String: Any]) -> Any? { nil }
}
Now let’s implement our modules utilizing a simplified model based mostly on the shape instance. 🤓
class A: Module {
func invoke(title: String, params: [String: Any]) -> Any? {
swap title {
case "example_form":
return self.exampleFormHook()
default:
return nil
}
}
non-public func exampleFormHook() -> [String] {
["Field 1", "Field 2", "Field 3"]
}
}
class B: Module {
func invoke(title: String, params: [String: Any]) -> Any? {
swap title {
case "example_form":
return self.exampleFormHook()
default:
return nil
}
}
non-public func exampleFormHook() -> [String] {
["Field 4", "Field 5"]
}
}
class C: Module {
func invoke(title: String, params: [String: Any]) -> Any? {
swap title {
case "example_form":
return self.exampleFormHook()
default:
return nil
}
}
non-public func exampleFormHook() -> [String] {
["Field 6"]
}
}
Subsequent we’d like a module supervisor that may be initialized with an array of modules. This supervisor will probably be answerable for calling the fitting invocation methodology on each single module and it will deal with the returned response in a type-safe method. We’ll implement two invoke methodology variations immediately. One for merging the end result and the opposite to return the primary results of a hook.
You possibly can attempt to implement a model that may merge Bool values utilizing the && operator
Right here is our module supervisor implementation with the 2 generic strategies:
struct ModuleManager {
let modules: [Module]
func invokeAllHooks<T>(_ title: String, sort: T.Sort, params: [String: Any] = [:]) -> [T] {
let end result = self.modules.map { module in
module.invoke(title: title, params: params)
}
return end result.compactMap { $0 as? [T] }.flatMap { $0 }
}
func invokeHook<T>(_ title: String, sort: T.Sort, params: [String: Any] = [:]) -> T? {
for module in self.modules {
let end result = module.invoke(title: title, params: params)
if end result != nil {
return end result as? T
}
}
return nil
}
}
You should use the the invokeAllHooks methodology to merge collectively an array of a generic sort. That is the one which we are able to use to collect all he kind fields utilizing the underlying hook strategies.
let manager1 = ModuleManager(modules: [A(), B(), C()])
let form1 = manager1.invokeAllHooks("example_form", sort: String.self)
print(form1)
let manager2 = ModuleManager(modules: [A(), C()])
let form2 = manager2.invokeAllHooks("example_form", sort: String.self)
print(form2)
Utilizing the invokeHook methodology you’ll be able to obtain an identical conduct just like the chain of accountability design sample. The responder chain works very comparable similiar, Apple makes use of responders on virtually each platform to deal with UI occasions. Let me present you the way it works by updating module B. 🐝
class B: Module {
func invoke(title: String, params: [String: Any]) -> Any? {
swap title {
case "example_form":
return self.exampleFormHook()
case "example_responder":
return self.exampleResponderHook()
default:
return nil
}
}
non-public func exampleFormHook() -> [String] {
["Field 4", "Field 5"]
}
non-public func exampleResponderHook() -> String {
"Good day, that is module B."
}
}
If we set off the brand new example_responder hook with the invokeHook methodology on each managers we’ll see that the result is kind of completely different.
if let worth = manager1.invokeHook("example_responder", sort: String.self) {
print(worth)
}
if let worth = manager2.invokeHook("example_responder", sort: String.self) {
print(worth)
}
Within the first case, since we have now an implementation in one among our modules for this hook, the return worth will probably be current, so we are able to print it. Within the second case there isn’t a module to deal with the occasion, so the block contained in the situation will not be executed. Instructed ya’, it is like a responder chain. 😜
