1.pod install失败

在执行pod install的时候会失败，提示如下：

[!] CocoaPods could not find compatible versions for pod "MJRefresh":
  In Podfile:
    MJRefresh (~> 3.5.0)

None of your spec sources contain a spec satisfying the dependency: `MJRefresh (~> 3.5.0)`.

You have either:
 * out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
 * mistyped the name or version.
 * not added the source repo that hosts the Podspec to your Podfile.

按提示执行pod install --repo-update之后，还是失败，提示：

[!] CocoaPods could not find compatible versions for pod "MJRefresh":
  In Podfile:
    MJRefresh (~> 3.5.0)

None of your spec sources contain a spec satisfying the dependency: `MJRefresh (~> 3.5.0)`.

You have either:
 * mistyped the name or version.
 * not added the source repo that hosts the Podspec to your Podfile.

两者的都是由于本地索引库没有更新到最新，找不到对应版本的spec文件，按如下方法执行：

// 以本地master的实际目录为准：
cd ~/.cocoapods/repos/master
Git pull

执行完这两个命令之后，再执行pod install即可，参考

不过以上方法可能比较耗时，并且下载了很长时间也会失败，这里推荐你使用第三步中的方法，方便不耗时！

2.cocoapods升级

执行：

sudo gem install cocoapods
sudo gem install -n /usr/local/bin cocoapods

3.SSL_ERROR_SYSCALL

提示：

error: RPC failed; curl 56 LibreSSL SSL_read: SSL_ERROR_SYSCALL, errno 60
fatal: the remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed

主要是cocoapods下载spec文件的速度太慢，个人喜欢到下面的地址直接下载，即Podfile文件的引入源。