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https://github.com/ulrikdamm/Forbind

Functional chaining and promises in Swift
https://github.com/ulrikdamm/Forbind

async binding monads promise result swift

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Functional chaining and promises in Swift

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# Forbind



Functional chaining and promises in Swift



Note: still in an experimental state. Everything could change. I would love some feedback on this. Write to [@ulrikdamm](https://twitter.com/ulrikdamm) on Twitter.



# What is it



Bind local or async expressions together functionally, all error handling taken care of for you:



```swift

func getUser(id : String) -> Promise> {

	let data = NSURL(string: id)

		=> { NSURLRequest(URL: $0) }

		=> NSURLConnection.sendRequest(.mainQueue())

		=> { response, data in data }

	

	return data

		=> NSJSONSerialization.toJSON(options: nil)

		=> { $0.dictionaryValue }

		=> User.fromJSON

}

```



• Bind operations together with =>



• No error handling inside your logic



• Transparent async calls



• No if-lets



• Combine inputs with ++



For more details, read my [Blog post](http://ufd.dk/blog/Binds-and-promises-with-Forbind).



## New in 1.1



• ResultPromise and OptionalPromise has been replaced with Promise> and Promise. Still works the same.



• You can use the bind operator to map over lists of promises!



```swift

let user = User(name: "Ulrik")

let names = user.loadFriends() => { $0.name } // [Promise]

```



• And you can also filter and reduce with filterp and reducep:



```swift

let someNames = filterp(names) { $0 != "Peter" } // Promise<[String]>

```



• The NSJSONSerialization extension now returns a JSONResult, which is either a Dictionary or Array.



# Get started



You can add Forbind to your project using [CocoaPods](https://cocoapods.org). Just add it to your Podfile:



```ruby

use_frameworks!



pod 'Forbind', '~> 1.1'

pod 'ForbindExtensions', :git => 'https://github.com/ulrikdamm/Forbind'

```



(You need the ```use_frameworks!``` since that feature of CocoaPods is still in beta. ForbindExtensions are optional)



Or you can add it using [Carthage](https://github.com/Carthage/Carthage) by adding this to your cartfile:



```

github "ulrikdamm/Forbind" ~> 1.0

```



This will add both Forbind.framework and ForbindExtensions.framework, which you can drag into your Xcode project.



Then in your files just import Forbind and optionally ForbindExtensions



```

import Forbind

import ForbindExtensions

```



The Forbind library is the bind operator (```=>```) and the combine operator (```++```), along with the Result enum and Promise classes.



ForbindExtensions are extensions to Foundation and UIKit for working better with Forbind, by, for example, returning a promise instead of using a completion block. The ForbindExtensions are still a work in progress, so you might want to make your own extensions instead. In this case, just only include the Forbind framework.



# What is the state of the project?



It’s still very experimental, so I would love some feedback on it. I wouldn’t recommend relying on this for product code yet. If you have a good idea, or just questions, submit a pull request or contact me at [@ulrikdamm](https://twitter.com/ulrikdamm) on Twitter.



Things that still needs to be considered:



• General direction of the project (are there some fundamental flaws?)



• Promise cancellation (support for cancelling an async operation if a promise is deallocated)



• Handling of dispatch queues (currently promise callbacks are run on the same queue as the operation finished on)



• More extensions for common UIKit/AppKit/Foundation methods to use Promise and Result instead of NSErrorPointer and completion blocks.



• "Expression was too complex to be solved in reasonable time" for big expressions.