Eventual

Simple implementation of an async value in swift.

Inside your services

func getUserFromInternet() -> Eventual<User> {
  let r = Resolver<User>()

  networkClient.get("whatever") { json in
    // do your json -> domain object
    let user: User = userFromJSON(json)
    r.resolve(user)
  }

  return r.eventual
}

Consuming your services

let eventualUser = getUserFromInternet()
eventualUser.finallyOnMainThread { user in
  // now you have a user!
}

You can also chain without losing type safety:

let nameEventual = eventualUser.then { user in user.firstName }
nameEventual.finallyOnMainThread { name in print(name) }

Or chain with other async operations:

func getReposForUser(user: User) -> Eventual<[Repo]> { ... }

let eventualRepos = getUserFromInternet().then{ user in getReposForUser(user) }

Convenient functions

join:

join(Eventual("hi"), Eventual(23)).finallyOnMainThread { tuple in
  print(tuple.0) // hi
  print(tuple.1) // 23
}

lift:

Convert functions from operating on concrete types to work on eventuals instead:

func add(lhs: Int, rhs: Int) -> Int {
    return lhs + rhs
}
// add is Int, Int -> Int
let liftedAdd = lift(add)
// liftedAdd is Eventual<Int>, Eventual<Int> -> Eventual<Int>
// the final value will be resolved as the addition of the two values once they resolve

UnsafeGetEventualValue:

This method is intended to help while testing, when you expect an Eventual to be resolved in a particular way. Use of this in production code is heavily discouraged as it sidesteps much of the point of the tool.

func testResolvesAfterWork() {
    let workDoer = WorkDoer()
    let eventual = workDoer.work()

    XCTAssertNil(UnsafeGetEventualValue(eventual))

    workDoer.finishWorking()

    XCTAssertEqual(UnsafeGetEventualValue(eventual), "work finished!")
}

Licensing

The MIT License (MIT)

Copyright (c) 2016 Zachary Clark

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.