Question

我想知道是否可以使用Swift从使用数组作为键的字典中获取值。

例如，假设我想获得一种食物的形象，但只有食物的名称，如apple。

var foodImages = [
    ["orange", "apple", "banana", "kiwi"] : UIImage(named: "fruit"),
    ["steak", "burger", "ground beef"]    : UIImage(named: "beef"),
    ["carrots", "mushrooms", "potatoes"]  : UIImage(named: "vegetable"),
]

如何使用该词典中的fruit获取apple的图片？

感谢任何帮助

Answer 1

不，因为钥匙必须是可以清洗的。您必须将每个项目设为不同的密钥：

var dict = [(String,String):String]()
dict["apple"] = "fruit"
dict["banana"] = "fruit"

Answer 2

嗯，你可以（如果它是NSArray），但它不会有效......

基本的想法是filter Dictionary具有自定义过滤功能的键，它会检查每个键以查看它是contains您要查找的项目。然后，由于filter返回Array，请取first中的Array项（如果存在）并使用作为关键字从Dictionary获取实际值。

最重要的是，Array中Dictionary作为关键字的唯一方法是NSArray。由于它是NSArray，因此您必须进行一些向下转换才能使事情正常进行。

它看起来像这样：

var foodImages = [
    ["orange", "apple", "banana", "kiwi"] : UIImage(named: "fruit"),
    ["steak", "burger", "ground beef"]    : UIImage(named: "beef"),
    ["carrots", "mushrooms", "potatoes"]  : UIImage(named: "vegetable"),
]

if let key = filter(foodImages.allKeys, { (list) -> Bool in
    let foodList = list as [String]
    return contains(foodList, "apple")
}).first as [String]? {
    if let image = foodImages[key] as UIImage? {
        /* use your image here */
    }
}

您可以轻松地将其作为一项功能：

func getFoodImage(food: String) -> UIImage? {
    if let key = filter(foodImages.allKeys, { (list) -> Bool in
        let foodList = list as [String]
        return contains(foodList, food)
    }).first as [String]? {
        if let image = foodImages[key] as UIImage? {
            return image
        }
    }
    return nil
}

let image = getFoodImage("apple")

话虽如此，使用NSArray作为Dictionary的关键词，你真的没有获得任何东西;只需将Array中的每个项目添加为自己的密钥并将UIImage存储为每个项目的值，就必须更好（并且效率更高）。由于UIImage是一个类，因此您将存储对它的引用而不是副本，因此内存使用不存在问题。

var foodImages: [String: UIImage] = []

let fruitImage = UIImage(named: "fruit")
let beefImage = UIImage(named: "beef")
let vegetableImage = UIImage(named: "vegetable")

for food in ["orange", "apple", "banana", "kiwi"] {
    foodImages[food] = fruitImage
}

for food in ["steak", "burger", "ground beef"] {
    foodImages[food] = beefImage
}

for food in ["carrots", "mushrooms", "potatoes"] {
    foodImages[food] = vegetableImage
}

然后它只是正常的Dictionary下标访问：

let image = foodImages["apple"]

image将为UIImage(named: "fruit")

按键数组访问字典值

2 个答案: