Ruby version and project not matching - ruby

Question

When I run, bundle I see the following:
Your Ruby version is 2.5.0, but your Gemfile specified
2.4.0.pre.dev
my Gemfile looks like:
source 'https://rubygems.org'
ruby '2.4.0-dev'
gem 'sinatra', :github => 'sinatra/sinatra'
This is my gem env:
$ gem env
RubyGems Environment:
- RUBYGEMS VERSION: 2.6.12
- RUBY VERSION: 2.5.0 (2017-07-31 patchlevel -1) [x86_64-darwin16]
- INSTALLATION DIRECTORY: /Users/johndoe/.rbenv/versions/2.4.0-dev/lib/ruby/gems/2.5.0
- USER INSTALLATION DIRECTORY: /Users/johndoe/.gem/ruby/2.5.0
- RUBY EXECUTABLE: /Users/johndoe/.rbenv/versions/2.4.0-dev/bin/ruby
- EXECUTABLE DIRECTORY: /Users/johndoe/.rbenv/versions/2.4.0-dev/bin
- SPEC CACHE DIRECTORY: /Users/johndoe/.gem/specs
- SYSTEM CONFIGURATION DIRECTORY: /Users/johndoe/.rbenv/versions/2.4.0-dev/etc
- RUBYGEMS PLATFORMS:
- ruby
- x86_64-darwin-16
- GEM PATHS:
- /Users/johndoe/.rbenv/versions/2.4.0-dev/lib/ruby/gems/2.5.0
- /Users/johndoe/.gem/ruby/2.5.0
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :backtrace => false
- :bulk_threshold => 1000
- "gem" => "-n/usr/local/bin"
- REMOTE SOURCES:
- https://rubygems.org/
- SHELL PATH:
- /Users/johndoe/.rbenv/versions/2.4.0-dev/bin
- /Users/johndoe/.rbenv/libexec
- /Users/johndoe/.nvm/versions/node/v8.1.4/bin
- /usr/local/sbin
- /Library/Frameworks/Python.framework/Versions/3.4/bin
- /Users/johndoe/.rbenv/shims
- /Users/johndoe/google-cloud-sdk/bin
- /Users/johndoe/Library/Python/2.7/bin
- /Users/johndoe/.rbenv/bin
- /usr/local/bin
- /usr/bin
- /bin
- /usr/sbin
- /sbin
When I type rbenv verions this is what I see:
system
2.0.0-p247
2.3.1
* 2.4.0-dev (set by /Users/johndoe/code/projects/blog-server/.ruby-version)
With Rbenv I am specifying the ruby version I want, and I am matching this in my project's Gemfile. However, whenever I run bundle or bundle exec gem uninstall sinatra I see the above error message about my ruby version and my gemfile ruby version not matching. I also see that my Ruby version is 2.5.0, and I have no idea how that got set. Can someone help me resolve this error?
Your Ruby version is 2.5.0, but your Gemfile specified
2.4.0.pre.dev
In my bash profile, I have:
export PATH=$HOME/.rbenv/bin:$PATH
....
eval "$(rbenv init -)"
In short, I just want the shell that runs my ruby process for my blog project to use ruby version 2.4.0-dev, and I am struggling to see understand what's blocking me and how to resolve it.
UPDATE:
I also noticed something odd. My bundler version continues to point to ruby 2.5.0p-1.
## Environment
Bundler 1.15.3
Rubygems 2.6.12
Ruby 2.5.0p-1 (2017-07-31 revision 59454) [x86_64-darwin16]
Git 2.11.0
Platform x86_64-darwin-16
OpenSSL OpenSSL 1.0.2k 26 Jan 2017
```
## Gemfile
### Gemfile
```ruby
source 'https://rubygems.org'
ruby '2.4.0-dev'
gem 'sinatra', '2.0.0'
```
### Gemfile.lock
```
<No /Users/johndoe/code/projects/blog-server/Gemfile.lock found>

Answer 1

In a project folder run:
rbenv local 2.4.0-dev
It should do the trick. You just need to specify local ruby version for this particular project. And your global version is set to 2.5.0

Answer 2

The best option here, I think, is to install Ruby Version Manager (rvm).
RVM helps every ruby developer by doing exactly what you need; manage ruby version automatically as you need.
Here's the link, hope it helps;
https://rvm.io/
Cheers