install & init
gem install bundler
bundler -v
bundle init # Gemfileを生成
このようなエラー
NoMethodError: private method `open' called for Gem::Package:Class
bundler gemのヴァージョンが古いから
gem install bundler
で解決
Gemfile
version specifiers
~>指定子
~> 2.0.3 = >= 2.0.3 and < 2.1
~> 2.1 = >= 2.1 and < 3.0
~> 2.2.betaは match prerelease versions like 2.2.beta.12