What is this variable-function hybrid thing?

Question

Created Oct ’20

Replies 2

Boosts 0

Participants 2

Code Block var sum: Double {
		let peopleCount = Double(numberOfPeople + 2)
		let tipSelection = Double(tipPercentages[tipPercentage])
		let orderAmount = Double(checkAmount) ?? 0
		return orderAmount / peopleCount * tipSelection
	}

Is this a function, a variable, or both?

Answered by Claude31 in 639413022

This is a computed var.

you invoke simply by a direct call.

Code Block print("sum is", sum)

When you use the var, the closure is executed and returns the computed value in the var itself.

The equivalent func would be

Code Block func sum() -> Double {		
  let peopleCount = Double(numberOfPeople + 2)		
  let tipSelection = Double(tipPercentages[tipPercentage])
  let orderAmount = Double(checkAmount) ?? 0		
  return orderAmount / peopleCount * tipSelection	
}

Code Block print("sum is", sum())

With a func you can add parameters, what you can't do with computed var

Code Block func sum(numberOfPeople: Int) -> Double {		
  let peopleCount = Double(numberOfPeople + 2)		
  let tipSelection = Double(tipPercentages[tipPercentage])
  let orderAmount = Double(checkAmount) ?? 0		
  return orderAmount / peopleCount * tipSelection	
}

Boost

Answer 1

Claude31 OP

Oct ’20

Accepted Answer

This is a computed var.

you invoke simply by a direct call.

Code Block print("sum is", sum)

When you use the var, the closure is executed and returns the computed value in the var itself.

The equivalent func would be

Code Block func sum() -> Double {		
  let peopleCount = Double(numberOfPeople + 2)		
  let tipSelection = Double(tipPercentages[tipPercentage])
  let orderAmount = Double(checkAmount) ?? 0		
  return orderAmount / peopleCount * tipSelection	
}

Code Block print("sum is", sum())

With a func you can add parameters, what you can't do with computed var

Code Block func sum(numberOfPeople: Int) -> Double {		
  let peopleCount = Double(numberOfPeople + 2)		
  let tipSelection = Double(tipPercentages[tipPercentage])
  let orderAmount = Double(checkAmount) ?? 0		
  return orderAmount / peopleCount * tipSelection	
}

1

Answer 2

TurtleLover OP

Oct ’20

Thanks, Claude31. This computed variable thing is new to me.

0