let studentsAndscores = ["Amy": 88, "James": 55, "Helen": 99]
Then your function should print 99.
But you don't know what the scores are, so your program has to handle all possibilities!
Hint:
When you get the value out of a dictionary using a key, the value that comes out is an Optional!
也就是说此时你需要用
let amyScore = studentsAndscores["Amy"]! 解包为Int类型的值 ，然后才能进行比较。
另一个示例：
class ViewController: UIViewController {
let eggTime:[String: Int] = [
"Soft":5,
"Medium":7,
"Hard":12
]
@IBAction func hardnessSelected(_ sender: UIButton) {
print(sender.currentTitle!)
let hardness = sender.currentTitle!
print(eggTime[hardness]!)
}
}
来源：oschina
链接：https://my.oschina.net/falcon10086/blog/3163066