我有一个包含3个对象的数组,就像这样:
class AClass {
var distance: Int?
}
let obj0 = AClass()
obj0.distance = 0
let obj1 = AClass()
obj1.distance = 1
let obj2 = AClass()
obj2.distance = 2
let arr = [obj0, obj1, obj2]
当我将数组缩小并将其赋值给一个变量时,我只能对数组中的最后一个元素求和。let total = arr.reduce(0, {$1.distance! + $1.distance!}) //returns 4
如果我尝试 $0.distance!,它会出现“expression is ambiguous without more context”的错误提示。我尝试更加明确:
var total = arr.reduce(0, {(first: AClass, second: AClass) -> Int in
return first.distance! + second.distance!
})
但是这个错误是 "'Int' is incompatible with contextual type '_'"
我该如何将它缩减到距离的总和?
arr.flatMap
会创建一个中间数组(可以使用arr.lazy.flatMap
避免),因此在这种情况下,另一种解决方案可能更可取。 - Martin R