在Swift 3.0中生成隨機字節

Question

我想在Swift 3.0中使用SecRandomCopyBytes生成隨機字節。這裏是我是如何做的雨燕在2.2

private static func generateRandomBytes() -> String? { 
    let data = NSMutableData(length: Int(32)) 

    let result = SecRandomCopyBytes(kSecRandomDefault, 32, UnsafeMutablePointer<UInt8>(data!.mutableBytes)) 
    if result == errSecSuccess { 
     return data!.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0)) 
    } else { 
     print("Problem generating random bytes") 
     return nil 
    } 
} 

在斯威夫特3，我試圖做這樣的，因爲我知道unsafemutablebytes的概念現在是不同的，但它不會讓我回來。如果我註釋掉返回部分，還在說Generic Parameter ResultType could not be inferred

fileprivate static func generateRandomBytes() -> String? { 
    var keyData = Data(count: 32) 
    _ = keyData.withUnsafeMutableBytes {mutableBytes in 
     let result = SecRandomCopyBytes(kSecRandomDefault, keyData.count, mutableBytes) 
     if result == errSecSuccess { 
      return keyData.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0)) 
     } else { 
      print("Problem generating random bytes") 
      return nil 
     } 
    } 
    return nil 
} 

有誰知道如何解決這一問題？

感謝

Answer 1

你接近，但return瓶蓋內從封閉返回 ，而不是從外部函數。 因此只有SecRandomCopyBytes()應在 閉包中調用，並且結果傳回。

func generateRandomBytes() -> String? { 

    var keyData = Data(count: 32) 
    let result = keyData.withUnsafeMutableBytes { 
     (mutableBytes: UnsafeMutablePointer<UInt8>) -> Int32 in 
     SecRandomCopyBytes(kSecRandomDefault, keyData.count, mutableBytes) 
    } 
    if result == errSecSuccess { 
     return keyData.base64EncodedString() 
    } else { 
     print("Problem generating random bytes") 
     return nil 
    } 
} 

對於「單表達閉合」的閉合類型可自動推斷 ，所以這可以縮短到

func generateRandomBytes() -> String? { 

    var keyData = Data(count: 32) 
    let result = keyData.withUnsafeMutableBytes { 
     SecRandomCopyBytes(kSecRandomDefault, keyData.count, $0) 
    } 
    if result == errSecSuccess { 
     return keyData.base64EncodedString() 
    } else { 
     print("Problem generating random bytes") 
     return nil 
    } 
}