带有字典的 Swift Playground 太慢

Question

我在 Xcode 7.1 中使用以下代码创建了一个 Swift Playground，它的评估速度非常慢(通常需要几分钟)。为什么会发生这种情况？由于它使 Playground 基本上无法使用，我可以采取什么措施来缩短其执行时间吗？

let sets = [
    "TEMPERATURE":[
        (value:37.0, attributes:["A":0.0, "B":0.2]),
        (value:37.5, attributes:["A":0.0, "B":1.0]),
        (value:38.0, attributes:["A":0.2, "B":0.5]),
        (value:38.5, attributes:["A":0.5, "B":0.2]),
        (value:39.0, attributes:["A":0.8, "B":0.0]),
        (value:39.5, attributes:["A":1.0, "B":0.0]),
        (value:40.0, attributes:["A":1.0, "B":0.0]),
    ],
    "VARIATION":[
        (value:0.0, attributes:["A":0.0, "B":1.0]),
        (value:2.0, attributes:["A":0.2, "B":0.8]),
        (value:5.0, attributes:["A":0.5, "B":0.5]),
        (value:8.0, attributes:["A":0.8, "B":0.2]),
        (value:10.0, attributes:["A":1.0, "B":0.0]),
    ]
]

Answer 1

这里的问题是 Swift 编译器在推导集合的类型时非常慢。如果您将类型明确化，Swift 编译器将不必花费任何时间来推导它。试试这个:

let sets: [String:[(value: Double, attributes:[String:Double])]] = [
    "TEMPERATURE":[
        (value:37.0, attributes:["A":0.0, "B":0.2]),
        (value:37.5, attributes:["A":0.0, "B":1.0]),
        (value:38.0, attributes:["A":0.2, "B":0.5]),
        (value:38.5, attributes:["A":0.5, "B":0.2]),
        (value:39.0, attributes:["A":0.8, "B":0.0]),
        (value:39.5, attributes:["A":1.0, "B":0.0]),
        (value:40.0, attributes:["A":1.0, "B":0.0]),
    ],
    "VARIATION":[
        (value:0.0, attributes:["A":0.0, "B":1.0]),
        (value:2.0, attributes:["A":0.2, "B":0.8]),
        (value:5.0, attributes:["A":0.5, "B":0.5]),
        (value:8.0, attributes:["A":0.8, "B":0.2]),
        (value:10.0, attributes:["A":1.0, "B":0.0]),
    ]
]