升級Xcode8.0Beta版，看著公司Swift版本的專案200多個報紅，那種酸爽也就蘋果能給。慢慢改吧！改的東西很多，但基本都不難，記錄幾個花費較長時間的Bug。

NO.1

【報錯】“Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be configured correctly for targets which use Swift. Use the [Edit > Convert > To Current Swift Syntax…] menu to choose a Swift version or use the Build Settings editor to configure the build setting directly.

【解決方法】設定 Build Settings —-> Use Legacy Swift Language Version —-> YES/NO，改為NO或者YES

NO.2

【問題】控制檯打印出大量無用的資訊。

【解決方法】在 Environment Variables中新增欄位 name:OS_ACTIVITY_MODE,value:disable

NO.3

【問題】整個專案能編譯通過，但在執行時啟動頁出現後就黑屏

【解決方法】問題在於，AppDelegate中didFinishLaunchingWithOptions這個方法沒有走。雖然是利用系統提供的修復，自動從Swift2.3修復到Swift3，但修復完的這個方法也還是不對的。

private func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { }

修改為

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool { }

NO.4

【報錯】“ambiguous referenc to member datask(with: completionhandler:)”

【解決方法】這個是在URLSessionDataTask中遇到的，屬於型別不明確的報錯。

修改前的程式碼：

let task: URLSessionDataTask = session.dataTask(with: request) { (data, resp, err) in   }

修改後的程式碼:

let task: URLSessionDataTask = session.dataTask(with: request as URLRequest) { (data, resp, err) in }
// 由於request是NSMutableURLRequest型別，在request 後面添加了 as URLRequest

NO.5

【報錯】”Cannot pass immutable value of type ‘NSDate?’ as inout argument”

【解決方法】var beginDate: NSDate? = NSDate()

修改前的程式碼：

var beginDate:  Date?
var endDate: Date?
let calendar: Calendar = Calendar.current
let ok: Bool = calendar.range(of: Calendar.Unit.month, start: &beginDate, interval: &interval, for: newDate as Date)

修改後的程式碼：

var beginDate:  NSDate? = NSDate()
var endDate: NSDate? = NSDate()
let calendar: Calendar = Calendar.current
let ok: Bool = calendar.range(of: Calendar.Unit.month, start: &beginDate, interval: &interval, for: newDate as Date)

NO.6

【警告】”Expression of type “UIViewController?” is unused”.

【解決】Swift3之前，每個方法都有一個預設的可以廢棄的結果。

相關解決例項：

// 例一：
    _ = navigationController?.popViewController(animated: true)

// 例二：
    t_principal.mas_makeConstraints { (make) in
            _ = make?.top.mas_equalTo()(0)
            _ = make?.left.mas_equalTo()(20)
            _ = make?.height.mas_equalTo()(self.frame.size.height / 3 - 1)
            _ = make?.width.mas_equalTo()(self.frame.size.width / 2 - 30)
        }

相關參考