用于测试对象是否存在于 Swift 数组中的简写? [英] Shorthand to test if an object exists in an array for Swift?

问题描述

目前，我有一个这样的对象数组:

Currently, I have an array of objects like this:

var myArr = [
  MyObject(name: "Abc", description: "Lorem ipsum 1."),
  MyObject(name: "Def", description: "Lorem ipsum 2."),
  MyObject(name: "Xyz", description: "Lorem ipsum 3.")
]

在继续之前，我正在测试对象是否存在:

I am testing if an object exists before proceeding like this:

let item = myArr.filter { $0.name == "Def" }.first
if item != nil {
  // Do something...
}

但我正在寻找一种更短的方法来做到这一点，因为我经常这样做.我想做这样的事情，但它是无效的:

But I'm looking for a shorter way to do this since I am doing this a lot. I'd like to do something like this but it is invalid:

if myArr.contains { $0.name == "Def" } {
  // Do something...
}

是否有我遗漏的速记语法或更好的方法?

Is there any shorthand syntax I'm missing or a better way to do this?

推荐答案

为什么不使用内置的 contains() 函数?有两种口味

Why not use the built-in contains() function? It comes in two flavors

func contains<S : SequenceType, L : BooleanType>(seq: S, predicate: @noescape (S.Generator.Element) -> L) -> Bool
func contains<S : SequenceType where S.Generator.Element : Equatable>(seq: S, x: S.Generator.Element) -> Bool

第一个将谓词作为参数.

and the first one takes a predicate as argument.

if contains(myArr, { $0.name == "Def" }) {
    println("yes")
}

更新:从 Swift 2 开始，两个全局 contains() 函数都有被协议扩展方法取代:

Update: As of Swift 2, both global contains() functions have been replaced by protocol extension methods:

extension SequenceType where Generator.Element : Equatable {
    func contains(element: Self.Generator.Element) -> Bool
}

extension SequenceType {
    func contains(@noescape predicate: (Self.Generator.Element) -> Bool) -> Bool
}

第一个(基于谓词的)用作:

and the first (predicate-based) one is used as:

if myArr.contains( { $0.name == "Def" }) {
    print("yes")
}

Swift 3:

if myArr.contains(where: { $0.name == "Def" }) {
    print("yes")
}

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