Swift  —  @escaping

在 Swift 3 中, closures 預設為 ＠noescape 的形式, 並將 Swift 2中的 noescape 關鍵字 deprecated。

// Swift 3
class HealthKitManager: NSObject {
 private let healthStore = HKHealthStore()
 func requestAuthorization(completion:  @escaping (Bool, Error?) -> Void) {
        var shareTypes = Set<HKSampleType>()
        var readTypes = Set<HKSampleType>()
        // Add Workout Type
        shareTypes.insert(HKSampleType.workoutType())
        readTypes.insert(HKSampleType.workoutType())
        // Request Authorization
        healthStore.requestAuthorization(toShare: shareTypes, read:  readTypes, completion: completion)
 }
}

Escaping Closures

A closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. When you declare a function that takes a closure as one of its parameters, you can write @escapingbefore the parameter’s type to indicate that the closure is allowed to escape.