/////////// Functions as first-class citizens /////////////////
/// Example 1: function as parameter
// Input: a and b as 2 integers to be added up
// Output: returns the sum
func foo(_a:Int,_b:Int) ->Int{
returna+b
}
func boo(function: (Int,Int) ->Int,_a:Int,_b:Int) ->Int{
returnfunction(a, b)
}
boo(function:foo,3,4)
/// Example 2: function as return type
func stepBackwards(_location:Int) ->Int{
return location-1
}
func stepForwards(_location:Int) ->Int{
return location+1
}
func chooseDirection(_enegyLevel:Int) -> (Int) ->Int{
if enegyLevel>10{
return stepBackwards
}
return stepForwards
}
func chooseDirectionAsClosure(_enegyLevel:Int) -> (Int) ->Int{
if enegyLevel>10{
return{ locationinreturnlocation-1}
}
return{ locationinreturnlocation+1}
}
var energyLevel = 12
let moveNearToTen: (Int) -> Int = chooseDirection(energyLevel)
var currentEnergy: Int { return moveNearToTen(energyLevel) }
while energyLevel > 10 {
energyLevel = currentEnergy
}
Swift简单的Closure例子(Simple Closure Examples in Swift)
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