I believe an important part of the development process is getting a working version into the hands of others. As part of this, being able to install the latest and greatest on the fly is paramount. It took me a lot of time to find a reliable way to build, sign, and distribute apps as part of this internal continuous delivery.

Continue reading “Automating iOS app builds” →

In an iOS app, localization can be especially difficult when dealing with attributed strings. Fairly often, designers request something like:

Read our Terms of Service, Privacy Policy, or contact us with any questions.

or like:

Searching for burgers in SOMA, San Francisco, CA:

The golden rule of localized strings is to treat them as atomic units:

• Never concatenate strings to form sentences. Many languages have different sentence structure or gender rules than English and you cannot just substitute a single word or phrase in for any other.
• Never use substrings for searching in an original string. If you depend on the standalone translation of “Privacy Policy” matching the sentence version, you will likely find translators do not understand this intent. You may also find the same search term multiple times (imagine if the user searched for “Search”).

Often these complexities are cited as reasons to avoid localization. But, unless you have geographic constraints, you will find a substantially larger audience with a localized application.

ZSWTappableLabel and ZSWTaggedString are two open-source libraries I have released to help solve these problems.

ZSWTappableLabel makes links inside your attributed strings tappable, as the name suggests. It’s a UILabel subclass which does not do any drawing itself, making it fast and easy.

ZSWTaggedString is the powerhouse. It transforms an HTML-like syntax into an attributed string. You can read more about the syntax and advanced usage on its GitHub page, but here’s how you might use it for the examples above:

Read our <i><tos>Terms of Service</tos></i>, <i><privacy>Privacy Policy</privacy></i>, or <i><contact>contact us</contact></i> with any questions.

Searching for <term>%@</term> in <location>%@</location>:

In my experience, localizers¹ are familiar enough with HTML to have no issues with localizing these strings. By marking the regions you intend to be visually distinct, they can more easily understand your intent, producing better localizations.

While on the subject, here are a few best practices for localization in iOS:

• To handle the current locale changing, or the dynamic type setting changing, reload your UI when observing:
  • NSCurrentLocaleDidChangeNotification
  • UIContentSizeCategoryDidChangeNotification
• To represent dates, durations, distances, lengths, etc., use an appropriate formatter.
• To create your own date formats, use +dateFormatFromTemplate:options:locale: on NSDateFormatter. Remember that these need recreating if the locale changes.
• To combine a first and last name, use ABPersonGetCompositeNameFormatForRecord with a temporary ABPersonRef, or use the new NSPersonNameComponentsFormatter.
• For sending non-user-facing data to a server, use en_US_POSIX as your locale.

  Read more tips and tricks at NSHipster about NSLocalizedString and NSLocale.

Conventional wisdom for creating a JPEG version of a UIImage is first to turn it into an NSData and immediately write it to disk like so:

NSData *jpegRepresentation = UIImageJPEGRepresentation(image, 0.94);
[jpegRepresentation writeToFile:outputURL.path
                     atomically:NO];

Most of the time this is exactly right. However, if file size is important, Image IO is a great alternative. It is a powerful system framework to read and write images, and produces smaller files at the same compression level.

Why Image IO?

A project I am working on requires uploading photos en masse. Low upload bandwidth makes file size a limiting factor, so I sought out ways to reduce it.

I put together a test project to find the differences between the two methods. The results are pretty interesting:

• Image IO files are on average 20% (but up to 30%) smaller¹.
• Image IO takes about 2x longer.

The only discernable visual difference is the grain in the images, but even that is minor. Here’s a diff between two versions of the original photo. The changes are nearly all in the grain.

Using Image IO

First, you’ll need to add two new framework dependencies:

@import ImageIO; // to do the actual work
@import MobileCoreServices; // for the type defines

When creating your JPEG file, the first step is to create a CGImageDestinationRef specifying where to write the result:

CGImageDestinationRef destinationRef = 
CGImageDestinationCreateWithURL((__bridge CFURLRef)outputURL,
                                /* file type */ kUTTypeJPEG,
                                /* number of images */ 1,
                                /* reserved */ NULL);

Image IO is able to produce files of a few different types² but my focus here is JPEGs. Next, we set up the properties of the output file, specifying a constant compression factor:

NSDictionary *properties = @{
  (__bridge NSString *)kCGImageDestinationLossyCompressionQuality: @(0.94)
};

CGImageDestinationSetProperties(destinationRef,
                                (__bridge CFDictionaryRef)properties);

And, importantly, we specify what is to be written out:

CGImageDestinationAddImage(destinationRef,
                           /* image */ image.CGImage,
                           /* properties */ NULL);

And finally, we write it to disk and clean up the reference:

CGImageDestinationFinalize(destinationRef);
CFRelease(destinationRef);

Xcode’s Editor > Structure menu has a few great actions:

These actions all act on either your cursor position or selection.

Balance Delimiter

Normally you can double-click quotes, brackets, or parenthesis to select the matching character and all text in-between. The Balance Delimiter behaves similarly: it looks at your cursor position (or selection), finds the nearest pair and selects in-between.

This doesn’t have a default keyboard shortcut, but you can set one up in Xcode’s Key Bindings preferences. I set it to ⇧⌃I since I use it in similar ways to Re-Indent.

Re-Indent ⌃I

Objective-C is a fairly indentation-heavy language, and Xcode generally does a good job at indenting while you’re typing. However, if you’re pasting text or refactoring things can get pretty hairy, so let Xcode fix up your code for you with Re-Indent.

Shift Left ⌘[, Shift Right ⌘]

You can also indent manually using the Shift Left and Shift Right actions, which unindent or indent by one tab, respectively. They do exactly what they say on the tin.

Move Line Up ⌥⌘[, Move Line Down ⌥⌘]

These actions move your current line (or selection) up or down by one line. Simple, right? What’s really useful is that it is context-aware: they understand going in and out of control flow or blocks. Much faster than cutting, pasting and re-indenting each time.

Comment Selection ⌘/

Rather than wrapping your code in /* … */ and dealing with the conflicting multi-line comments you probably already have, simply select what you want to temporarily eliminate and hit the shortcut. Each line selected is then prefixed by //.

My first experience programming was making webpages seventeen years ago at the age of ten. It was amazing: by just typing some words and strange markup into a text editor I could create exactly what anyone else could! A bunch of documents magically turned into websites.

Continue reading “How I started programming” →

From the Programming with Objective-C (backup) overview from Apple:

When dealing with errors passed by reference, it’s important to test the return value of the method to see whether an error occurred, as shown above. Don’t just test to see whether the error pointer was set to point to an error.

and from the Error Handling Programming Guide (backup):

Success or failure is indicated by the return value of the method. Although Cocoa methods that indirectly return error objects in the Cocoa error domain are guaranteed to return such objects if the method indicates failure by directly returning nil or NO, you should always check that the return value is nil or NO before attempting to do anything with the NSError object.

For example, let’s say we’re executing a fetch request:

NSError *error = nil;
NSFetchRequest *request = /* … */;
NSArray *objects = [context executeFetchRequest:request
                                          error:&error];

To test if the fetch was successful, we must do:

if (objects) {
    // hooray!
} else {
    NSLog(@"Got an error: %@", error);
}

A method taking an NSError ** does not guarantee how it is used when successful. In this case, even a successful method call may end up with error set to something other than nil.