Can NSArray contain nil?
Can NSArray contain nil?
arrays can’t contain nil. There is a special object, NSNull ( [NSNull null] ), that serves as a placeholder for nil.
How do you declare NSArray in Objective C?
In Objective-C, the compiler generates code that makes an underlying call to the init(objects:count:) method. id objects[] = { someObject, @”Hello, World!”, @42 }; NSUInteger count = sizeof(objects) / sizeof(id); NSArray *array = [NSArray arrayWithObjects:objects count:count];
What is the difference between NSArray and array?
Array is a struct, therefore it is a value type in Swift. NSArray is an immutable Objective C class, therefore it is a reference type in Swift and it is bridged to Array . NSMutableArray is the mutable subclass of NSArray . Because foo changes the local value of a and bar changes the reference.
What is the type of nil in Swift?
In Swift, nil means the absence of a value. Sending a message to nil results in a fatal error. An optional encapsulates this concept. An optional either has a value or it doesn’t.
What is Nsnull in Swift?
A singleton object used to represent null values in collection objects that don’t allow nil values. iPadOS 2.0+ macOS 10.0+
Is it faster to iterate through an NSArray or an NSSet?
Yes, NSArray is faster than NSSet for simply holding and iterating. As little as 50% faster for constructing and as much as 500% faster for iterating.
What is the difference between NSString and string?
NSString is a class Swift is interoperatable with Objective-C and converts some Objective-C types to Swift types. Types that can be converted between Obj-C and Swift are known as bridged types. String and NSString are example of such bridged types and hence you can assign NSString to a String variable.
Does copy increase retain count?
No, a copied object will have a retain count of 1, just like a newly initialized object.