Directly from Apple: The NSNull class defines a singleton object you use to represent null values in situations where nil is prohibited as a value (typically in a collection object such as an array or a dictionary). So in your example, that’s exactly what’s happening, the programmer is choosing to put a null object into … Read more
You can use the as? operator, which returns an optional value (nil if the downcast fails) if let latestValue = sensor[“latestValue”] as? String { cell.detailTextLabel.text = latestValue } I tested this example in a swift application let x: AnyObject = NSNull() if let y = x as? String { println(“I should never be printed: \(y)”) … Read more
A small modification to the method can make it recursive: @interface NSDictionary (JRAdditions) – (NSDictionary *) dictionaryByReplacingNullsWithStrings; @end @implementation NSDictionary (JRAdditions) – (NSDictionary *) dictionaryByReplacingNullsWithStrings { const NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary: self]; const id nul = [NSNull null]; const NSString *blank = @””; for (NSString *key in self) { const id object = [self … Read more
I’ve made a few changes to Jacob’s original answer to extend it to handle dictionaries and arrays stored within the original dictionary. #import “NSDictionary+NullReplacement.h” #import “NSArray+NullReplacement.h” @implementation NSDictionary (NullReplacement) – (NSDictionary *)dictionaryByReplacingNullsWithBlanks { const NSMutableDictionary *replaced = [self mutableCopy]; const id nul = [NSNull null]; const NSString *blank = @””; for (NSString *key in self) … Read more
The NULL value for Objective-C objects (type id) is nil. While NULL is used for C pointers (type void *). (In the end both end up holding the same value (0x0). They differ in type however.) In Objective-C: nil (all lower-case) is a null pointer to an Objective-C object. Nil (capitalized) is a null pointer … Read more
nil is the literal null value for Objective-C objects, corresponding to the abstract type id or any Objective-C type declared via @interface. For instance: NSString *someString = nil; NSURL *someURL = nil; id someObject = nil; if (anotherObject == nil) // do something Nil is the literal null value for Objective-C classes, corresponding to the … Read more
They differ in their types. They’re all zero, but NULL is a void *, nil is an id, and Nil is a Class pointer.