ios – 在Swift 3.0中生成随机字节

我想在 Swift 3.0中使用SecRandomcopyBytes生成随机字节.这是我在Swift 2.2中的表现

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Swift 3中,我尝试这样做,因为我知道unsafemutablebytes的概念现在不同了,但它不允许我返回.如果我注释掉返回部分,它仍然说无法推断通用参数ResultType

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
}

有谁知道如何解决这一问题？

谢谢

解决方法

你很接近,但在关闭内部返回
从封闭,而不是从外部功能.
因此,只应在中调用SecRandomcopyBytes()
关闭,结果传回来.

func generaterandomBytes() -> String? {

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

对于“单表达闭包”,闭包类型可以推断
自动,所以这可以缩短为

func generaterandomBytes() -> String? {

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