uninitialized constant ActiveRecord::ConnectionAdapters::ConnectionManagement - ruby

Question

Im currently working on a sinatra app, and im having a trouble regarding postgresql connection to sinatra, im try to execute this command:
rake db:create
to create the database but it throws this error.
C:\Users\John\Documents\Registration_Sinatra>rake db:create
rake aborted!
NameError: uninitialized constant ActiveRecord::ConnectionAdapters::ConnectionManagement
C:/Users/John/Documents/Registration_Sinatra/app/app.rb:2:in `<top (required)>'
C:/Users/John/Documents/Registration_Sinatra/Rakefile:1:in `<top (required)>'
LoadError: cannot load such file -- sinatra/activerecord
C:/Users/John/Documents/Registration_Sinatra/app/app.rb:2:in `<top (required)>'
C:/Users/John/Documents/Registration_Sinatra/Rakefile:1:in `<top (required)>'
(See full trace by running task with --trace)
this is my app.rb
require 'sinatra'
require 'sinatra/activerecord'
require 'pg'
require './config/environments'
class RegistrationSinatra < ActiveRecord::Base
end
get '/' do
erb :index
end
this is my environments.rb
configure :development do
#DEFAULT_CONN = {database: 'development_registration_sinatra', user: 'postgres', password: 'secret123', host: 'localhost'}
db = URI.parse(ENV['DATABASE_URL'] || "postgres://#{#DEFAULT_CONN[:host]}/#{#DEFAULT_CONN[:database]}?user=#{#DEFAULT_CONN[:user]}")
ActiveRecord::Base.establish_connection(
:adapter => db.scheme == 'postgres' ? 'postgresql' : db.scheme,
:host => #DEFAULT_CONN[:host],
:username => #DEFAULT_CONN[:user],
:password => #DEFAULT_CONN[:password],
:database => db.path[1..-1],
:encoding => 'utf8')
end
this is my gemfile
source 'https://rubygems.org'
ruby "2.2.2"
gem 'sinatra'
gem 'activerecord'
gem 'sinatra-activerecord'
gem 'tux'
gem 'pg'
and my Rakefile
require './app/app'
require 'sinatra/activerecord/rake'
hope you guys can pin point what's wrong with my sample app so i can progress thanks.

Answer 1

Here is the solution: https://github.com/janko-m/sinatra-activerecord/pull/66
In your Gemfile, add:
gem "activerecord", "< 5.0.0"
run bundle update and it will work.