Question

获得如下所示的错误：

var products = [
    ("Kayak", "A boat for one person", "Watersports", 275.0, 10),
    ("Lifejacket", "Protective and fashionable", "Watersports", 48.95, 14)]

let stockTotal = products.reduce(0,{(total, product) -> Int in return total + product.4}); //missing argument label 'combine:' in call

在我看过reduce的所有例子中，都没有使用联合收割机标签：

let numbers = Array(1...10)
.reduce("numbers: ") {(total, number) in total + "\(number) "}

那么我做错了什么？

Answer 1

如果使用尾随闭包，则可以省略标签：

var products = [
    ("Kayak", "A boat for one person", "Watersports", 275.0, 10),
    ("Lifejacket", "Protective and fashionable", "Watersports", 48.95, 14)
]

let stockTotal = products.reduce(0) { $0 + $1.4 }

使用尾随闭包，在最终)之后将闭包提供给函数。如果您不想使用尾随闭包，则需要添加参数标签：

let stockTotal2 = products.reduce(0, combine: { $0 + $1.4 })

Answer 2

使用尾随闭包语法：

let stockTotal = products.reduce(0) {(total, product) -> Int in return total + product.4}

缺少参数标签＆＃39;合并：＆＃39;在电话中

2 个答案: