Question

Apple在Swift 2中引入了新的错误处理

https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html#//apple_ref/doc/uid/TP40014216-CH7-ID10

我正在使用AFNetoworking v2.x的项目，其中AFHTTPRequestSerializer有2个选择器：

- (NSMutableURLRequest *)requestWithMethod:(NSString *)method
                             URLString:(NSString *)URLString
                            parameters:(id)parameters DEPRECATED_ATTRIBUTE;

- (NSMutableURLRequest *)requestWithMethod:(NSString *)method
                             URLString:(NSString *)URLString
                            parameters:(id)parameters
                                 error:(NSError * __autoreleasing *)error;

首先弃用，但第二个由Swift 2编译器自动转换为第一个签名。现在不允许使用老式方法：

var error: NSError?
let request = self!.operationManager.requestSerializer.requestWithMethod(method, URLString: url?.absoluteString, parameters: params, error: error)

给了我一个编译时错误：

Cannot convert value of type 'NSError?' to expected argument type '()'

但是全新的表示法会将选择器与错误处理减少到没有它的弃用变体。

do {
    let request = try
    self!.operationManager.requestSerializer.requestWithMethod(method, URLString: url?.absoluteString, parameters: params)
} catch let error as NSError {
    // ...
}

Swift 2中解决此问题的最佳做法是什么？在这种情况下有没有办法指定某个选择器？

UPD：Swift 2功能的更精确链接成为我问题的原因。 https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/AdoptingCocoaDesignPatterns.html#//apple_ref/doc/uid/TP40014216-CH7-ID10

Answer 1

似乎这在Xcode 7.1中正常工作（我记得在7.0中有这个问题）只是改变你的方法使用错误指针，即&error

var error: NSError?
let request = self!.operationManager.requestSerializer.requestWithMethod(method, URLString: url?.absoluteString, parameters: params, error: &error)

Answer 2

Swift 2更喜欢仅为必要的方法提供Try Catch块。因此，如果您的方法有可能需要错误处理的情况，那么只提供此块。

do {    
   try managedObjectContext.save() 
} catch {

   // Replace this implementation with code to handle the error appropriately.

   // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

   let NSError = error as NSError

   NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
   abort()
}

Swift 2中明确的老式错误处理

2 个答案: