FutureKit extensions with some convenience methods.

Future+Then.swift

import Foundation
import FutureKit

extension Future {
    // Executes the block iff the future is successful and leaves the result immutable
    public final func then(executor : Executor, block: T throws -> Void) -> Future<T> {
        return onSuccess(executor) { (result: T) -> Completion<T> in
            do {
                try block(result)
                return .Success(result)
            }
            catch let error {
                return .Fail(error)
            }
        }
    }
    public final func then(block: T throws -> Void) -> Future<T> {
        return then(.Primary, block: block)
    }
}

Future+Throws.swift

import Foundation
import FutureKit

extension Future {
    public final func onSuccessTry<__Type>(executor: Executor, block:(result:T) throws -> __Type) -> Future<__Type> {
        return onSuccess(executor) { result -> Completion<__Type> in
            do {
                let blockResult = try block(result: result)
                return .Success(blockResult)
            }
            catch let error {
                return .Fail(error)
            }
        }
    }
    
    public final func onSuccessTry<__Type>(block:(result:T) throws -> __Type) -> Future<__Type> {
        return onSuccess { result -> Completion<__Type> in
            do {
                let blockResult = try block(result: result)
                return .Success(blockResult)
            }
            catch let error {
                return .Fail(error)
            }
        }
    }
}

Future+Void.swift

import Foundation
import FutureKit

extension Future {
    /// Converts the current future to a Future<Void>, ignoring any result.
    /// Useful for combining different Futures if you don't care about the results
    func toVoid() -> Future<Void> {
        return onSuccess { result -> Void in
            return ()
        }
    }
}