CocoaPods could not find compatible versions for pod

最近開始用Swift 4開發，想當然third party也要用到最新，以Alamofire、PKHUD為例，我分別需要4.7版、5.0版

        根據Alamofire官方、PKHUD官方pod file應該是
        pod 'Alamofire', '~>  4.7'
        pod 'PKHUD', '~> 5.0'

        

結果pod install會遇到如下錯誤
        [!] CocoaPods could not find compatible versions for pod "Alamofire":
        In Podfile:
           Alamofire (~> 4.7)
        None of your spec sources contain a spec satisfying the dependency: `Alamofire (~> 4.7)`.

        

實際上用pod search也的確是找不到Alamofire 4.7版、PKHUD 5.0版，解決方式參考CocoaPods Guides - The Podfile的From a podspec in the root of a library repo.
修正後的pod file為
        pod 'Alamofire', :git => 'https://github.com/Alamofire/Alamofire.git', :tag => '4.7.0'
        pod 'PKHUD', :git => 'https://github.com/pkluz/PKHUD.git', :branch => 'release/swift4'

   

再pod install成功執行如下