Tag: Programming

Although in normal cases, you should be specific in defining data types, swift offers Any, AnyObject, and AnyHashable.

Any can represent an instance of any type, including functions, instance of a class, struct, or enum, it’s more general than AnyObject, where AnyObject is a protocol all classes indirectly conform to.

AnyObject is useful when using Objetive-C / Swift, some parts of Objective-C use this protocol to enhance compatibility with Swift, it’s equivelant to ‘id’ in Objective-C.

so, when to use Any / AnyObject ?
say you have a dictionary..

let anyStuff: [Any] = [1,”z”,3,[]]

If your data will be used only in Swift code, then you should use Any because your types (Int, Double, Float, String, Array, and Dictionary) are not objects.

If it will be passed to Objective-C code that expect an NSDictionary, then go with AnyObject.

AnyHashable is a super-type that is defined as a struct, it was introduced in Swift 3 standard library, it’s used to bring untyped sets and dictionaries from Objective-C to Swift.

public struct Notification : ReferenceConvertible, Equatable, Hashable {
    /// Storage for values or objects related to this notification.
    public var userInfo: [AnyHashable : Any]?
}

Swift is strongly typed, data should either be explicitly assigned or inferred, the main basic data types that come with swift are

Type	Description
Character	a 16-bit Unicode character like “a” or “/”
String	represents textual data like “Hello”
Float	represents 32-bit floating-point number
Double	represents 64-bit floating-point number
Bool	logical value: true or false
Tuples	groups multiple values in single value
Int	integer, a whole number
UInt	unsigned integer, a whole number
Int8	1 byte integer
Int32	4 bytes integer
Int64	8 bytes integer
UInt8	1 byte unsigned integer
UInt32	4 bytes unsigned integer
UInt64	8 bytes unsigned integer

On a 32-bit device, Int has the size of Int32, on 64-bit devices, Int has the size of Int64, same goes for UInt.

Swift has a feature where it can infer the type of the data directly, for example the variable level here is infered to be an Int

var level = 12

you can explicitly determine the type directly

var level: Int = 17

Extra Tip: A CGFloat holds either 32-bits of data or 64-bits of data depending on the CPU Architecture.

Any meaningful program should contain stores to save data, swift distinguishes between constant and variable pieces of data with let and var keywords, for example, say you have a customer object, their birthdate is a constant, but their balance is a variable, if you declare data as a constant, the compiler will not allow you to have it changed later, even at compile time, this is not only for safety, but constants are generally faster to work with by the processor.

class Customer {
	let id = 22034
	let birthdate = "11/11/2011"
	var balance = 109.3
}

Constants cannot change after you run your app, they prevent accidental breakage of a value that should not change.