Why is RoR not installed?

Question

Ruby on Rails

Goodnight! Can you please tell me why the rail is not installed?) It says Error installing rails: activesupport requires Ruby version >= 2.2.2. I have ruby ​​installed 2.0 How to upgrade? (OS X)
I wrote:
ruby ​​-e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install... "
rbenv install 2.4.0
Then I wrote ruby -v and for some reason it gave me 2.0, although in theory it should be 2.4.0

Answer 1

rbenv install 2.4.0
rbenv global 2.4.0
ruby ​​-v #test ruby ​​changing

Answer 2

I advise you to look at RVM: rvm.io