撸一个便捷带bug的PromiseKit

今天我们梳理了PromiseKit，于是我们根据原理和流程大体撸一个PromiseKit，大家感受一下其中的思维逻辑

enum Result<T>{

case pending

case resolved(T)

}

class Box<T>{

func inspect(b: (T)->Void){

}

func seal(_ :T)->Void{

}

}

class ABox<T>: Box<T>{

var value:Result<T>

init(value: T ) {

self.value = Result.resolved(value)

}

override func inspect(b: (T) -> Void) {

switch value {

case .pending:

break

case .resolved(let v):

b(v)

break

default:

print("none")

}

}

override func seal(_: T) {

print("seal",self,value)

}

}

protocol Able{

associatedtype T

func pipe(to:(Result<T>)->Void)

}

class A<T>: Able{

var box:ABox<Result<T>>

init(_ v:Result<T>) {

self.box = ABox.init(value: v)

}

func pipe(to:(Result<T>)->Void){

box.inspect { (v:Result<T>) in

to(v)

}

}

}

extension Able{

func then<U:Able>(_ body:(T)->U) -> A<U.T>{

let next = A<U.T>.init(.pending)

pipe { (v:Result<T>) in

print(v)

switch v {

case .pending:

print("then pending")

break

case .resolved(let value):

print(value)

let rv = body(value)

rv.pipe(to: next.box.seal)

break

}

}

return next

}

func map<U>(_ transform:(T)->U) -> A<U>{

let next = A<U>.init(.pending)

pipe { (v:Result<T>) in

switch v {

case .pending:

break

case .resolved(let value):

next.box.seal(Result.resolved(transform(value)))

break

}

}

return next

}

}

var a:A<String> = A.init(.resolved("AAAAAA"))

func firstyl<U>(exec body:()->U) -> A<U.T> where U:Able{

let rp = A<U.T>.init(.pending)

print("firstly")

body().pipe(to: rp.box.seal)

return rp

}

firstyl { () -> A<String> in

return A<String>.init(Result<String>.resolved("A"))

}.then { (msg:String) -> A<Int> in

print("msg", msg)

return A<Int>.init(Result<Int>.resolved(1))

}

func ax<T>(a:T){

print("ax", a)

}

func bx<T>(value:T, _ b:(T)->Void){

b(value)

print("bx")

}

bx(value: "ax",ax)