Programming in Swift: Functions & Types

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

Part 2: Closures

12. Closure Syntax

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Previous episode: 11. Challenge: Closures Next episode: 13. Challenge: Closure Syntax

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Notes: 12. Closure Syntax

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’ve got the basic idea, let’s look at couple more special features of closures. Closures are meant to be more lightweight than functions. They’re really great alternatives to functions you wouldn’t get a lot of reuse out of.

let longClosure 

let longClosure 😺= { (a: Int, b: Int) 
}

let longClosure = { (a: Int, b: Int) 😺-> Int in

  a * b

let noParameterTypes

let noParameterTypes😺: Operate

let noParameterTypes: Operate = { (a❌: Int❌, b❌: Int❌) -> Int in

let 😺noReturnType

let noReturnType: Operate = { (a, b) in

let shortClosure: Operate = {...

let shortClosure: Operate = { $0 * $1 }

longClosure(4, 2)
noParameterTypes(4, 2)
noReturnType(4, 2)
shortClosure(4, 2)

let voidClosure: () -> Void

let voidClosure: () -> Void 😺= { () -> Void in
  
}😺

let voidClosure: () -> Void = { ❌() -> Void in❌
  😺print("Yay, Swift!")🛑
}

let voidClosure: () -> 😺()🛑

let voidClosure: 😺Void -> Void🛑

let voidClosure: 😺()🛑 -> Void

voidClosure()

printResult(10, 3, { $0 * $1 + 10 })

printResult(10, 3, operate: (Int, Int) -> Int)

printResult(10, 3) 💛{ (<#Int#>, <#Int#>) -> Int in
  <#code#>
}💛

printResult(10, 3💛) {💛 

printResult(10, 3) { 😺$0 * $1 + 10🛑 }

Button("Add") {
  let priorityIndex = self.taskStore.getIndex(for: self.priority)
  self.taskStore.prioritizedTasks[priorityIndex].tasks.append(
    Task(name: self.text)
  )
        
  self.presentationMode.wrappedValue.dismiss()
}

Button(
  action: { self.modalIsPresented = true }
) {
  Image(systemName: "plus")
}

Button(
  action: { self.modalIsPresented = true }
) {
  Image(systemName: "plus")
}

Button(
  action: { self.modalIsPresented = true },
  label: { Image(systemName: "plus") }
)

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