Multipeer Connectivity
Multipeer Connectivity (introduced in iOS 7) lets nearby iPhones, iPads, and Macs talk directly to each other using Wi-Fi, peer-to-peer Wi-Fi, or Bluetooth. No internet, no server, no central service required.
Swift
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NSNotification & NSNotificationCenter
NSNotificationCenter acts as a central hub. Any part of an app can send notices or listen for changes from others. Observers sign up for certain events and get a callback when they happen.
NSPredicate
NSPredicate is a Foundation class that defines logical conditions to fetch or filter data. Its syntax mixes SQL WHERE clauses with regex for expressive queries on collections.
NSExpression
NSExpression is a class in Cocoa that simplifies complex data tasks. It evaluates mathematical expressions, such as 4 + 5 - 2**3, which gives 1.
NSUUID /CFUUIDRef /UIDevice -uniqueIdentifier /-identifierForVendor
Apple stopped letting apps use the unique device identifier, called UDID, from iOS 5 onwards. Apple blocked new apps using it after May 2013.
NSCoding / NSKeyedArchiver
Apple gives options like Core Data or NSKeyedArchiver with NSKeyedUnarchiver. These turn objects into data and back again.
MKLocalSearch
MKLocalSearch lets your app search for places (restaurants, shops, etc.) using normal language, all powered by Apple’s own data.
NSSecureCoding
NSSecureCoding is a protocol from iOS 6 / OS X Mountain Lion. It adds the class method supportsSecureCoding.
NSURLCache
NSURLCache is the built-in, automatic HTTP(S) cache used by NSURLConnection, NSURLSession (default/ephemeral configs), and WKWebView.
NSLocalizedString
NSLocalizedString is a macro in Foundation that gives a localised version of a string. It takes a key to find the string and a comment to help translators.
KVC Collection Operators
The article discusses Key-Value Coding (KVC) Collection Operators in Objective-C, which provide a concise, Ruby-like syntax for performing aggregate operations on collections using valueForKeyPath:.
NSOrderedSet
NSOrderedSet is not a subclass of NSSet due to problems with Objective-C's single inheritance and the mutable/immutable class pairs in Foundation's class clusters.
NSURLProtocol
NSURLProtocol is the most powerful (and least-known) piece of Apple’s URL Loading System.
NSLinguisticTagger
NSLinguisticTagger offers powerful tools to process natural language. It breaks strings into tokens, finds parts of speech and stems, pulls out names of people, places, and groups, and spots languages and scripts.
AddressBookUI
The Address Book UI framework in iOS, used alongside AddressBook.framework, provides controllers for managing contacts but includes a uniquely valuable function, ABCreateStringWithAddressDictionary(), which formats address components into a localised string.
CFBag
The article explores the CFBag and CFMutableBag Core Foundation types, which implement a bag (multi-set) data structure, allowing multiple occurrences of elements with associated counts.
CFStringTransform
NSString and its toll-free bridged counterpart CFMutableString in Foundation and Core Foundation are highlighted for their exceptional Unicode handling, with CFStringTransform enabling powerful string transformations like stripping diacritics, naming Unicode characters, and transliterating between scripts such as Latin, Cyrillic, and Hiragana.
NSSortDescriptor
NSSortDescriptor is a Foundation class used to sort collections. It is created with a key (property to sort on), ascending (true for ascending order), and optionally a selector or comparator for comparisons.
NSCache
NSCache works like NSMutableDictionary but removes objects automatically when memory runs low. This saves you from handling memory warnings or setting up timers to clear space.
NSIndexSet
NSIndexSet and its mutable version, NSMutableIndexSet, form a sorted set of unique unsigned integers. They act like an NSRange that allows gaps.