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JavaScript evaluation isn’t limited to single statements. When you evaluate code that declares a function or variable, it’s saved into the context’s object space. context.evaluateScript(#""" function triple(number) { return number * 3; } """#) context.evaluateScript("triple(5)")? .toInt32() // 15 Handling Exceptions The evaluateScript(_:) method doesn’t expose an NSError ** pointer and isn’t impor

Written by Mattt December 29th, 2014 This article has been translated into: 中文 Cocoa is the de facto standard library of Objective-C, containing many of the essential frameworks for working in the language, such as Foundation, AppKit, and Core Data. Cocoa Touch is basically just Cocoa with UIKit substituted for AppKit, and is often used interchangeably with Cocoa to refer to the system frameworks

Written by Mattt December 1st, 2014 This article has been translated into: 中文 Everyone is excited about ᴡᴀᴛᴄʜ. Developers especially. What’s the best way to get started? Look no further than Apple’s WatchKit developer resources. Watch the “Getting Started” video—it’s like being in Moscone. Read the Human Interface Guidelines—consider it a prerequisite for designing your application. Peruse the Wa

Written by Nate Cook November 17th, 2014 This article has been translated into: 中文 With all the different means to comment, mark up, save, and share right at our fingertips, it’s easy to overlook the value of a printed sheet of paper. UIKit makes it easy to print straight from a user’s device with custom designs that you can adapt to both your content and the paper size. This article will first wa

Written by November 10th, 2014 This article has been translated into: 中文 For as long as the iPhone has existed, location services have been front and center. Maps.app was one of the killer features that launched with the original iPhone. The Core Location API has existed in public form since the first public iPhone OS SDK. With each release of iOS, Apple has steadily added new features to the fram

In many ways, the story of Apple has been about fusing together technologies through happy accidents of history to create something better than before: OS X as a hybrid of MacOS & NeXTSTEP. Objective-C as the combination of Smalltalk’s OOP paradigm and C. iCloud as the byproduct of MobileMe and actual clouds (presumably). While this is true for many aspects of Apple’s technology stack, inter-proce

We’ve discussed the importance of how events are communicated in APIs previously in our article on Key-Value Observing. This week, we’ll expand our look at the available options, with NSNotificationCenter & NSNotification. NSNotificationCenter provides a centralized hub through which any part of an application may notify and be notified of changes from any other part of the application. Observers

Written by Mattt October 6th, 2014 This article has been translated into: 中文 While it’s not accurate to say that Swift is “Objective-C without the C”, it’s for lack of resemblance to Objective-C, not the absence of C. Swift is vehemently not C. Swift certainly draws inspiration from Haskell, Rust, Python, D, and other modern languages, but one can perhaps best understand the language as a rejectio

Written by Mattt September 30th, 2014 This article has been translated into: 中文 Did you know that UIAlertView and UIActionSheet (as well as their respective delegate protocols) are deprecated in iOS 8? It’s true. ⌘-click on UIAlertView or UIActionSheet in your code, and check out the top-level comment: UIAlertView is deprecated. Use UIAlertController with a preferredStyle of UIAlertControllerStyle

Yesterday’s article described various techniques for resizing images using APIs from the UIKit, Core Graphics, Core Image, and Image I/O frameworks. However, that article failed to mention some rather extraordinary functionality baked into the new Photos framework which takes care of all of this for you. For anyone developing apps that manage photos or videos, meet your new best friend: PHImageMan

Since time immemorial, iOS developers have been perplexed by a singular question: “How do you resize an image?” It’s a question of beguiling clarity, spurred on by a mutual mistrust of developer and platform. Myriad code samples litter Stack Overflow, each claiming to be the One True Solution™ — all others, mere pretenders. In this week’s article, we’ll look at 5 distinct techniques to image resiz

Written by Mattt November 7th, 2018 (revised) This article has been translated into: français Objective-C uses the NS_OPTIONS macro to define option types, or sets of values that may be combined together. For example, values in the UIViewAutoresizing type in UIKit can be combined with the bitwise OR operator (|) and passed to the autoresizingMask property of a UIView to specify which margins and d

Written by Mattt September 2nd, 2014 This article has been translated into: 中文 Swift was announced 3 months ago to the day. For many of us, it was among the most shocking and exciting events in our professional lives. In these intervening months, it’s safe to say our collective understanding and appreciation of the language has evolved and changed significantly. First came the infatuation period.

Written by Mattt July 25th, 2018 (revised) This article has been translated into: 한국어 iOS has a complicated relationship with the web. And it goes back to the very inception of the platform over a decade ago. Although the design of the first iPhone seems like a foregone conclusion today, the iconic touchscreen device we know and love today was just one option on the table at the time. Early protot

Written by Mattt August 22nd, 2018 (revised) This article has been translated into: 한국어 In 1911, linguist Franz Boas observed that speakers of Eskimo–Aleut languages used different words to distinguish falling snowflakes from snow on the ground. By comparison, English speakers typically refer to both as “snow,” but create a similar distinction between raindrops and puddles. Over time, this simple

Written by Mattt October 3rd, 2018 (revised) This article has been translated into: 中文 What would a program be without operators? A mishmash of classes, namespaces, conditionals, loops, and namespaces signifying nothing. Operators are what do the work of a program. They are the very execution of an executable; the teleological driver of every process. Operators are a topic of great importance for

Although iOS 8 and Swift has garnered the lion’s share of attention of the WWDC 2014 announcements, the additions and improvements to testing in Xcode 6 may end up making some of the most profound impact in the long-term. This week, we’ll take a look at XCTest, the testing framework built into Xcode, as well as the exciting new additions in Xcode 6: XCTestExpectation and performance tests. Most Xc

Written by Mattt June 16th, 2014 This article has been translated into: 中文 Diagnostics combine logic with analytics to arrive at a conclusion. It’s science and engineering at their purest. It’s human reasoning at its most potent. Within the medical profession, a diagnosis is made through instinct backed by lab samples. For industrial manufacturing, one diagnoses a product fault through an equal ap

Written by Mattt June 9th, 2014 This article has been translated into: 中文 Ask anyone, and they’ll tell you: WWDC 2014 was one of the most exciting in recent memory. It was, first and foremost, a developer event, with nary a hardware announcement to upstage the latest software & developer tools. And boy howdy, was there a lot to be excited about. The announcements from iOS 8 & OS X Yosemite alone w

Written by Mattt May 26th, 2014 This article has been translated into: 中文 Civilization is built on infrastructure: roads, bridges, canals, sewers, pipes, wires, fiber. When well thought-out and implemented, infrastructure is a multiplying force that drives growth and development. But when such formative structures are absent or ad hoc, it feels as if progress is made in spite of the situation. It

Written by Mattt May 19th, 2014 This article has been translated into: 中文 Abstractions are necessary for doing meaningful work, but they come at a cost. To work at a high level is to turn a blind eye to nonessential details in order to reason with larger logical chunks. Determining what information is important within a particular context, however, is challenging, and is at the heart of performanc

In programming, what often begins as a necessary instruction eventually becomes a vestigial cue for humans. In the case of Objective-C, #pragma directives, method type encodings, and all but the most essential storage classes have been rendered essentially meaningless, as the compiler becomes increasingly sophisticated. Discarded and disregarded during the compilation phase, they nonetheless remai

On iOS, UIActivityViewController provides a unified interface for users to share and perform actions on strings, images, URLs, and other items within an app. You create a UIActivityViewController by passing in the items you want to share and any custom activities you want to support (we’ll show how to do that later on). You then present that view controller as you would any other modal or popover.

Apple is nothing if not consistent. From Pentalobular screws to Sandboxing, customers are simply expected to relinquish a fair amount of control when they choose to buy a Mac or iPhone. Whether these design decisions are made to ensure a good user experience, or this control is exercised as an end in itself is debatable, but the reality is that in both hardware and software, Apple prefers an ivory

As consumer web technologies and enterprises race towards cloud infrastructure, there is a curious and significant counter-movement towards connected devices. In this age of mobile computing, the possibilities of collaboration, whether in work or play, have never been greater. In this age of privacy concerns and mass surveillance, the need for secure, ad hoc communications has never been more pres

Written by Mattt February 24th, 2014 This article has been translated into: 中文 Why the hell is everything NS-whatever? You’ll hear that within the first minute of introducing someone to Objective-C. Guaranteed. Like a parent faced with the task of explaining the concept of death or the non-existence of Santa, you do your best to be forthcoming with facts, so that they might arrive at a conclusion

Written by Mattt July 24th, 2012 This article has been translated into: 中文 Sorting: it’s the mainstay of Computer Science 101 exams and whiteboarding interview questions. But when was the last time you actually needed to know how to implement Quicksort yourself? When making apps, sorting is just something you can assume to be fast, and utility is a function of convenience and clarity of intention.