What does this mean? Variable declared followed by a block without assignment

Question

Noob Swift question--I can\'t figure out what this means in Swift:

public var currentTime: NSTimeInterval? {
    return self.audioPlayer?.currentTime
}


        

Answer 1

This is called Read-Only Computed Properties

According to Apple Docs

A computed property with a getter but no setter is known as a read-only computed property. A read-only computed property always returns a value, and can be accessed through dot syntax, but cannot be set to a different value.

For more info Computed Properties

Answer 2

It is the same as:

public var currentTime: NSTimeInterval? {
    get { return self.audioPlayer?.currentTime }
}

When your computed property only has a get, you can omit the word get and the curly brackets.

From the swift guide:

You can simplify the declaration of a read-only computed property by removing the get keyword and its braces:

Answer 3

I wrote a little playground for clarification:

//: Computed properties

import UIKit

var variable_int = 1

var computed_int: Int {
get { return 1 }
set { newValue }
}

var get_only_int: Int {
  return 1
}

var get_only_int_2: Int {
get { return 1 }
}

variable_int = 2 // legal
computed_int = 2 // legal

// computed_read_only_int = 2   // 'computed_read_only_int' is a get-only property
// computed_read_only_int_2 = 2 // 'computed_read_only_int_2' is a get-only property


// This is another way to specify a variable you could find useful, I found it somewhere on natashatherobot.com
var variable_int_2: Int = {
  return 1
}()

variable_int_2 = 2 // legal

works in Xcode 8.1