All the dynamism of Ruby complicates the autocomplete. So much so that the rubistas are already accustomed to not having a tool of code Completion as has Java and C#.
When there is no language proficiency or API, in your case the Gems, which is working, Vim ends up losing to the Ides.
Still, there are some tools that bring the autocomplete for Ruby, as is the case with Solargraph. Just install Gem using gem install solargraph
and install the plugin for Vim, which is still in beta. It also has the extension for Visual Studio Code. Just have Gem installed in the system.
Everything gets even more complicated when you are using Rails, which makes the autoload of the files at runtime. Solargraph often does not see this require
and can’t do the autocomplete.
If you are using Docker, Gem must be installed locally, not within container.
pro vscode has https://github.com/castwide/vscode-solargraph
– Danilo Cândido