When I tried to create a migration file, I was told that the Ruby version was different from the one specified in the Gemfile, and I could not execute it.
$ bin/rails g migration hoge Your Ruby version is 2.4.6, but your Gemfile specified 2.6.4
Make sure rbenv is installed.
$ which rbenv /usr/local/bin/rbenv
Install the specified Ruby version.
$ rbenv install 2.6.4 Downloading openssl-1.1.1g.tar.gz... -> https://dqw8nmjcqpjn7.cloudfront.net/ddb04774f1e32f0c49751e21b67216ac87852ceb056b75209af2443400636d46 Installing openssl-1.1.1g... Installed openssl-1.1.1g to /Users/tamu/.rbenv/versions/2.6.4 Downloading ruby-2.6.4.tar.bz2... -> https://cache.ruby-lang.org/pub/ruby/2.6/ruby-2.6.4.tar.bz2 Installing ruby-2.6.4... ruby-build: using readline from homebrew Installed ruby-2.6.4 to /Users/tamu/.rbenv/versions/2.6.4
Confirm that it has been installed.
$ rbenv versions system * 2.4.6 (set by /Users/tamu/.rbenv/version) 2.6.4
This time, I wanted to apply it only under a specific directory, so specify as follows.
$ rbenv local 2.6.4
Confirm that it has switched.
$ ruby -v ruby 2.6.4p104 (2019-08-28 revision 67798) [x86_64-darwin18]