减少数组以在 Swift 中设置

问题描述

我试图在 Swift 中将对象数组减少为一个集合，这是我的代码:

I am trying to reduce an array of objects to a set in Swift and this is my code:

objects.reduce(Set<String>()) { $0.insert($1.URL) }

但是，我收到一个错误:

However, I get an error:

Type of expression is ambiguous without more context.

我不明白问题出在哪里，因为 URL 的类型肯定是字符串.有什么想法吗?

I do not understand what the problem is, since the type of URL is definitely String. Any ideas?

推荐答案

你不必减少一个数组来把它变成一个集合；只需使用数组创建集合:let objectSet = Set(objects.map { $0.URL }).

You don't have to reduce an array to get it into a set; just create the set with an array: let objectSet = Set(objects.map { $0.URL }).

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