John John - 1 year ago 70
Swift Question

" if let " must be used only for optional ? (Swift)

Question 1: if let must be used only for optional

Question 2: If yes for question 1 , Does "if let " evaluate true or false or something ? Because we use this in a " if condition " and only way " if condition " works is to evaluate true or false. Here example :

var something:String? = " Hello "

if let makeSomethingNew = something {
let final = makeSomethingNew + something

let makeSomethingNew = something evaluates true here ?

Answer Source

Question 1

if let is knowns as optional binding.

It only works on Optionals. The following code would generate an error:

var str = "Hello, playground"

if let x = str {
    print("success") // error: initializer for conditional binding must have Optional type, not 'String'

Why? Because if let is only used for optionals, String is not an optional.


And yes it evaluates if the optional has been set ie has a value.

For more info see this answer

Additional question I am adding: Why are we doing such?

Because optionals are either set or not ( have a value or not). We want to only do something if they have a value. If they don't have a value, we don't want to do anything (we don't want to crash either).

You also use it to unwrap the optional.

var optionalString : String? = "hi"

if let unwraped = optionalString {
    print (unwraped) // hi | easier to work with
    print(optionalString) // Optional("hi") | not so easy to work with
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