我已经从 github克隆了这个 iOS 应用程序，并尝试按照文档中的说明运行carthagecarthage update。但是，当我这样做时，我收到一条错误消息（事实上，这是我的整个终端输出）：
Deans-MacBook-Air:SwiftWeather deang$ carthage update
*** Fetching SwiftyJSON
*** Fetching Alamofire
*** Checking out Alamofire at "1.3.1"
*** Checking out SwiftyJSON at "2.2.1"
*** xcodebuild output can be found in /var/folders/p0/chbxzj8920v2gwrqfcnb8p380000gn/T/carthage-xcodebuild.fdWo4D.log
*** Building scheme "Alamofire OSX" in Alamofire.xcworkspace
*** Building scheme "Alamofire iOS" in Alamofire.xcworkspace
** BUILD FAILED **
The following build commands failed:
Check dependencies
(1 failure)
Code Sign error: No code signing identities found: No valid signing identities (i.e. certificate and private key pair) matching the team ID “(null)” were found.
CodeSign error: code signing is required for product type 'Framework' in SDK 'iOS 8.4'
A shell task failed with exit code 65:
** BUILD FAILED **
The following build commands failed:
Check dependencies
(1 failure)
Deans-MacBook-Air:SwiftWeather deang$
Cartfile看起来像这样：
github "Alamofire/Alamofire"
github "SwiftyJSON/SwiftyJSON"
现在我不知道这是否特定于该项目（尽管我不这么认为，它很受欢迎，而且似乎没有其他人在抱怨）。所以我倾向于认为这是我做错了，或者我的环境有问题。