>>- (flatMap) (left associative)
public func >>- <A, B>(a: EventLoopFuture<A>, f: @escaping (A) -> EventLoopFuture<B>) -> EventLoopFuture<B> -<< (flatMap) (right associative)
public func -<< <A, B>(f: @escaping (A) -> EventLoopFuture<B>, a: EventLoopFuture<A>) -> EventLoopFuture<B> >=> Left-to-right Kleisli composition of monads (left associative)
public func >=> <A, B, C>(f: @escaping (A) -> EventLoopFuture<B>, g: @escaping (B) -> EventLoopFuture<C>) -> (A) -> EventLoopFuture<C> <=< Kleisli composition of monads (right associative)
public func <=< <A, B, C>(f: @escaping (B) -> EventLoopFuture<C>, g: @escaping (A) -> EventLoopFuture<B>) -> (A) -> EventLoopFuture<C> <^> (map) (left associative)
public func <^> <A, B>(a: EventLoopFuture<A>, f: @escaping (A) -> B) -> EventLoopFuture<B> <*> Applicative
public func <*> <A, B>(f: EventLoopFuture<((A) -> B)>, a: EventLoopFuture<A>) -> EventLoopFuture<B> func get(with client: RedisClient, for data: RedisData) -> Future<RedisData> {
return client.command("GET", [data])
}
private func terse(_ req: Request) throws -> Future<RedisResponse> {
let client = try req.make(RedisClient.self)
return get(with: client, for: "KEY")
>>- curry(get)(client)
>>- curry(get)(client)
>>- curry(get)(client)
<^> RedisResponse.init
}vs
private func nested(_ req: Request) throws -> Future<RedisResponse> {
let client = try req.make(RedisClient.self)
return client.command("GET", ["key"]).flatMap(to: RedisResponse.self) { data in
return client.command("GET", [data]).flatMap(to: RedisResponse.self) { data in
return client.command("GET", [data]).map(to: RedisResponse.self) { data in
return RedisResponse(data)
}
}
}
}>=> is a monadic version of function composition.
func query(with: String) -> EventLoopFuture<Int> {
return EventLoopFuture(2)
}
func updateCache(with id: Int) -> EventLoopFuture<String> {
return EventLoopFuture("Success")
}
let queryAndUpdate = query >=> updateCacheApplies a future function to a future value
Currying is the technique of translating the evaluation of a function that takes multiple arguments into evaluating a sequence of functions, each with a single argument.
let renderer: (String, Encodable) -> Future<View> = try req.make(LeafRenderer.self).render
curry(renderer) //(String) -> (Encodable) -> Future<View>
overview >>- curry(renderer)("overview")This is useful for using the operators with non unary functions.
.package(url: "https://github.com/John-Connolly/terse.git", from: "1.0.0")