mac解决方案。执行命令

sudo gem update    

然后按提示输入你的Mac密码

我使用参数——user-install运行以下命令:

gem install name_of_gem --user-install

Edit

There was one gem I still could not install (it required the Ruby.h headers of the Ruby development kit or something), then I tried the different version managers, but somehow that still did not really work as it was stated in the documentations how to just install and switch (it did just not switch the versions). Then I removed all the installed version managers and installed afterwards with brew install ruby the latest version and did set the PATH variable, too. (It will be mentioned after the installation of ruby from brew), which worked.

在用rbenv安装ruby之后，你还需要设置全局ruby。为此，你可以这样做，rbenv全球3.2.1，然后安装绑定器与gem安装绑定器。它会起作用的。

正如@idleberg提到的，在Mac OS上，最好安装rbenv，以避免手动安装ruby时出现权限错误。

安装

$ brew update
$ brew install rbenv

在.bashrc文件中添加以下内容:

eval "$(rbenv init -)"

现在，我们可以查看可供安装的ruby版本列表

$ rbenv install -l

以安装2.3.8版本为例

$ rbenv install 2.3.8

现在我们可以全局地使用这个ruby版本

$ rbenv global 2.3.8

最后运行

$ rbenv rehash

$ which ruby
/Users/myuser/.rbenv/shims/ruby
$ ruby -v
ruby 2.3.7p456 (2018-03-28 revision 63024) [x86_64-darwin17]

大胆尝试吧

现在安装捆扎器

$ gem install bundler

全部完成!

博士TL;

在一些情况下，我通过关闭终端会话并在重新尝试失败的命令之前打开一个新的会话来解决这类错误。

长解释

在一些SOs(如MacOS)中，已经预先安装了ruby的系统级版本。如果您正在使用版本管理器，例如rbenv或asdf，它们通过处理当前会话的环境来工作，以便相关命令指向版本管理器安装的二进制文件。

When installing a new binary, the version manager installs it in a special location, usually somewhere under the user's home directory. It then configures everything in your PATH so that you get the freshly installed binaries when you issue a command, instead of the ones that came with your system. However, if you don't restart the session (there are other ways of getting your environment updated, but that's the easiest one) you don't get the new configuration and you will be using the original installation.

对于最新的操作系统版本

首先运行sudo xcode-select——switch / Sudo gem install cocoapods—user-install

这对我很有用