Specs satisfying the `Alamofire (~ 4.2.0)` dependency were found, but they required a higher minimu

podfile文件 

platform :ios, ‘7.0’
use_frameworks!
target “swift” do
pod 'Alamofire', '~> 4.2.0'
pod 'MJRefresh', '~> 3.1.12'
pod 'SDWebImage', '~> 4.0.0-beta2'
pod 'SVProgressHUD', '~> 2.0.4'
end

用pod install  时  报错 

 Invalid `Podfile` file: Unsupported platform `iOS`. Platform must be `:ios`, `:osx`, `:tvos`, or `:watchos`..

[!] Unable to satisfy the following requirements:

- `Alamofire (~> 4.2.0)` required by `Podfile`

Specs satisfying the `Alamofire (~> 4.2.0)` dependency were found, but they required a higher minimum deployment target.

原因是Alamofire4.0.0最低支持9.0  ，把 platform :ios, ‘7.0’  改成platform :ios, ‘9.0’，就OK 了。

[!] The dependency `MBProgressHUD (~> 0.8)` is not used in any concrete target.