检查Swift字典是否不包含任何值? [英] Check If Swift Dictionary Contains No Values?

问题描述

所以我正在做一个待办事项列表应用程序，我希望在所有购物商品都被删除后得到通知.我有一本字典，其中包含String:store作为键和[String]:items作为值.有没有一种快速的方法来检查所有项目的数组是否为空?

So I'm making a to-do list app, and I want the user to be notified when all of the shopping items have been deleted. I have a dictionary that contains the String:store as a key and the [String]:items as the values. Is there a fast way to check if all of the items' arrays are empty?

推荐答案

有一种简单的方法:

dicts.values.flatten().isEmpty

但这将遍历所有列表，而没有任何快捷方式.通常，这实际上不是问题.但是，如果您要在发现一个非空值的情况下纾困:

But that will walk through all the lists without any shortcuts. Usually that's really not a problem. But if you want to bail out when you find a non-empty one:

func isEmptyLists(dict: [String: [String]]) -> Bool {
    for list in dicts.values {
        if !list.isEmpty { return false }
    }
    return true
}

当然，您可以使它更加通用，以实现快捷和便捷:

Of course you can make this much more generic to get short-cutting and convenience:

extension SequenceType {
    func allPass(passPredicate: (Generator.Element) -> Bool) -> Bool {
        for x in self {
            if !passPredicate(x) { return false }
        }
        return true
    }
}

let empty = dicts.values.allPass{ $0.isEmpty }

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