Programming in Swift: Functions & Types

Jan 4 2022 · Swift 5.5, iOS 15, Xcode 13

Part 2: Closures

14. forEach & map

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Previous episode: 13. Challenge: Closure Syntax Next episode: 15. compactMap & flatMap

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Notes: 14. forEach & map

Update Notes: This course was originally recorded in 2019. It has been reviewed and all content and materials updated as of October 2021.

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Now that you know a bit about closures, you’re ready to see how they can be particularly useful when dealing with collections. Collections in Swift have several handy methods that take a closure as an argument. These closures are executed for each element in the collection, much like the body of a for loop!

init(priority: Task.Priority, names: [String]) {
  self.init(
    priority: priority,
    tasks: names.map 💛{ Task(name: $0) }💛
  )
}

for price in prices {
  print(price)
}

prices

prices.forEach(

prices.forEach { (<#Double#>) in
  <#code#>
}

prices.forEach { (😺price🛑) in
  😺print(price)🛑
}

prices.forEach { ❌(price) in❌

prices.forEach { print(😺$0🛑) }

var arrayForSalePrices: [Double] = []

for price in prices {

}

  arrayForSalePrices.append(price * 0.9)

arrayForSalePrices

let salePrices = 

let salePrices = 😺prices.map { (<#Double#>) -> T in
  <#code#>
}

let salePrices = prices.map { (😺price❌) -> T in

let salePrices = prices.map { (price) -> 😺Double❌ in

let salePrices = prices.map { price -> Double in
  price * 0.9
}

let salePrices = prices.map { 😺$0 * 0.9🛑 }

let priceLabels

let priceLabels = salePrices.map {...

 (price) -> String in

String(format: "%.2f", price)