erica

import UIKit
import XCPlayground

class ViewController: UIViewController {
    func action() { print("Bing!") }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .whiteColor()
        

chriseidhof

// Variables just contain an integer. We can have a maximum of `Int.max` variables in our program.  ¯\_(ツ)_/¯

private struct Var {
    static var freshVarIx = 0
    let ix: Int
    init() {
        Var.freshVarIx+=1
        ix = Var.freshVarIx
    }
}

NachoSoto

//
//  Signal+Extensions.swift
//  Khan Academy
//
//  Created by Nacho Soto on 10/1/15.
//  Copyright © 2015 Khan Academy. All rights reserved.
//

import ReactiveCocoa

dvdsgl

A monad is a fancy word for a generic type of the form MyMonad<T> (a generic type of arity 1).

A monad is special because it adds 'special powers' to the T that it wraps. These 'special powers' won't sound very special to an imperative programmer, so you have to squint to see them but bear with me.

• IEnumerable<T> is a monad that gives values of type T the special power of nondeterminism, or the ability to 'be' multiple values at once.
• Nullable<T> is a monad that gives values of type T the special power of nullability, or the ability to be absent.
• Task<T> is a monad that gives values of type T the special power of asynchronicity, or the ability to be used before they are computed.

The trick with monads comes when you want to play with the T values, because they are inside another type. C# introduced language changes to make dealing with values inside these monads easier:

thanegill

//: Playground - noun: a place where people can play

// Got most of it from:
// https://developer.apple.com/sample-code/wwdc/2015/downloads/Crustacean.zip
// This is in the Protocol-Oriented Programming in Swift talk
// Pay special attention to the Heterogeneous Equality section, on page 2.
//
// Most comments directly copy/pasted from Crustacean Playground

protocol Account {

CodaFi

indirect enum Formula : CustomStringConvertible {
  case Var(String)
  case Or(Formula, Formula)
  case And(Formula, Formula)
  case Imply(Formula, Formula)
  case BiImply(Formula, Formula)
  case Negate(Formula)

  var description : String {
    switch self {

steipete

static NSData *PSPDFCalculateSHA256FromFileURL(NSURL *fileURL, CC_LONG dataLength, NSError **error) {
    NSCParameterAssert(fileURL);

    NSData *shaData;

    int fd = open(fileURL.path.UTF8String, O_RDONLY);
    if (fd < 0) {
        if (error) *error = [NSError pspdf_errorWithCode:PSPDFErrorCodeUnableToOpenPDF description:@"Failed to open file for calculating SHA256."];
        return nil;
    }

praeclarum

//
//  ArrayDiff.swift
//
//  Created by Frank A. Krueger on 6/30/15.
//  Copyright © 2015 Krueger Systems, Inc. All rights reserved.
//  License: MIT http://opensource.org/licenses/MIT
//

import Foundation

nicklockwood

Thoughts on Swift 2 Errors

When Swift was first announced, I was gratified to see that one of the (few) philosophies that it shared with Objective-C was that exceptions should not be used for control flow, only for highlighting fatal programming errors at development time.

So it came as a surprise to me when Swift 2 brought (What appeared to be) traditional exception handling to the language.

Similarly surprised were the functional Swift programmers, who had put their faith in the Haskell-style approach to error handling, where every function returns an enum (or monad, if you like) containing either a valid result or an error. This seemed like a natural fit for Swift, so why did Apple instead opt for a solution originally designed for clumsy imperative languages?

I'm going to cover three things in this post:

wincent

2015-01-29 Unofficial Relay FAQ

Compilation of questions and answers about Relay from React.js Conf.

Disclaimer: I work on Relay at Facebook. Relay is a complex system on which we're iterating aggressively. I'll do my best here to provide accurate, useful answers, but the details are subject to change. I may also be wrong. Feedback and additional questions are welcome.

What is Relay?

Relay is a new framework from Facebook that provides data-fetching functionality for React applications. It was announced at React.js Conf (January 2015).