前情提要
昨天我們在發布網站的過程中遇到了錯誤：
remote: In Gemfile:
remote: sqlite3
remote: !
remote: ! Failed to install gems via Bundler.
remote: ! Detected sqlite3 gem which is not supported on Heroku:
remote: ! https://devcenter.heroku.com/articles/sqlite3heroku：「ㄉㄅㄑ，我不會用 sqlite3。」
所以我們必須移除 sqlite3 這個套件才行。
認識 Gemfile
Gemfile 在專案的根目錄下：
第12行寫著：gem 'sqlite3' 表示這個專案會使用 sqlite3 這個套件。套件是一群佛心來的人寫好後公開給大家用的程式。如果你想要安裝套件，就會需要在這裡加一行程式，如果想要移除某個套件，就要刪掉那一行程式。
這裡有所有能裝的套件：https://rubygems.org/gems。如果你想要成佛也可以在這裡貢獻一下你的程式。
每當修改過 Gemfile 之後，你要在小黑框輸入 bundle install。 bundle 是一個管理套件的套件，他會幫你下載套件程式碼。
如果你輸入 bundle install 之後看到的是這樣：
D:\只要有心，人人都可以作卡米狗\ironman>bundle install
'bundle' 不是內部或外部命令、可執行的程式或批次檔。表示你的電腦沒有裝過 bundler，需要在小黑框輸入 gem install bundler 來安裝。
D:\只要有心，人人都可以作卡米狗\ironman>gem install bundler
Fetching: bundler-1.16.1.gem (100%)
Successfully installed bundler-1.16.1
Parsing documentation for bundler-1.16.1
Installing ri documentation for bundler-1.16.1
Done installing documentation for bundler after 20 seconds
1 gem installed 移除 rails 專案中所使用的 sqlite3 套件
我們開始進行 sqlite3 的移除工作吧。
前面提到 Gemfile 第12行寫著：gem 'sqlite3'，我們可以在這行的最前面加一個 # 號把這行變成註解，像這樣：
當然你要直接刪掉那行也不是不行啦，弄好之後記得存檔，存完檔之後，在小黑框輸入 bundle install。
D:\只要有心，人人都可以作卡米狗\ironman>bundle
Using rake 12.3.0
Using concurrent-ruby 1.0.5
Using i18n 0.9.1
Using minitest 5.10.3
Using thread_safe 0.3.6
Using tzinfo 1.2.4
Using activesupport 5.1.4
Using builder 3.2.3
Using erubi 1.7.0
Using mini_portile2 2.3.0
Using nokogiri 1.8.1 (x64-mingw32)
Using rails-dom-testing 2.0.3
Using crass 1.0.3
Using loofah 2.1.1
Using rails-html-sanitizer 1.0.3
Using actionview 5.1.4
Using rack 2.0.3
Using rack-test 0.8.2
Using actionpack 5.1.4
Using nio4r 2.2.0
Using websocket-extensions 0.1.3
Using websocket-driver 0.6.5
Using actioncable 5.1.4
Using globalid 0.4.1
Using activejob 5.1.4
Using mini_mime 1.0.0
Using mail 2.7.0
Using actionmailer 5.1.4
Using activemodel 5.1.4
Using arel 8.0.0
Using activerecord 5.1.4
Using public_suffix 3.0.1
Using addressable 2.5.2
Using bindex 0.5.0
Using bundler 1.16.1
Using byebug 9.1.0
Using xpath 2.1.0
Using capybara 2.16.1
Using ffi 1.9.18 (x64-mingw32)
Using childprocess 0.8.0
Using coffee-script-source 1.12.2
Using execjs 2.7.0
Using coffee-script 2.4.1
Using method_source 0.9.0
Using thor 0.20.0
Using railties 5.1.4
Using coffee-rails 4.2.2
Using multi_json 1.12.2
Using jbuilder 2.7.0
Using puma 3.11.0
Using sprockets 3.7.1
Using sprockets-rails 3.2.1
Using rails 5.1.4
Using rb-fsevent 0.10.2
Using rb-inotify 0.9.10
Using rubyzip 1.2.1
Using sass-listen 4.0.0
Using sass 3.5.4
Using tilt 2.0.8
Using sass-rails 5.0.7
Using selenium-webdriver 3.8.0
Using turbolinks-source 5.0.3
Using turbolinks 5.0.1
Using tzinfo-data 1.2017.3
Using uglifier 4.0.2
Using web-console 3.5.1
Bundle complete! 12 Gemfile dependencies, 66 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
D:\只要有心，人人都可以作卡米狗\ironman>你會看到目前專案正在使用的所有套件。
進行本機測試
開啟 rails server 看看是否一切正常：
D:\只要有心，人人都可以作卡米狗\ironman>rails s
=> Booting Puma
=> Rails 5.1.4 application starting in development
=> Run `rails server -h` for more startup options
*** SIGUSR2 not implemented, signal based restart unavailable!
*** SIGUSR1 not implemented, signal based restart unavailable!
*** SIGHUP not implemented, signal based logs reopening unavailable!
Puma starting in single mode...
* Version 3.11.0 (ruby 2.4.2-p198), codename: Love Song
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3000
Use Ctrl-C to stop看似正常，開網頁 http://localhost:3000/ 看卻發現：
他說：「你的程式有用到 sqlite3，但是你沒有安裝 sqlite3，所以我又爆啦。」
我們在那裡用到了 sqlite3？
我們在 config/database.yml 中使用了 sqlite3。
原來 sqlite3 是一個資料庫的套件，但是由於 heroku 不支援 sqlite3，所以我們必須找另一款 heroku 能支援的資料庫換上去，這裡我們要換的是 postgresql。
改用 postgresql
我們需要把 config/database.yml 中第 8 行的 adapter: sqlite3 改為 adapter: postgresql。
我們還需要安裝 postgresql 這個套件，這個套件叫 pg，所以修改 Gemfile 如下：
我在第 13 行寫 gem 'pg', '~> 0.21.0'，其實要寫在第幾行都行。不過第 37 行有一個 group：
group :development, :test do
# Call 'byebug' anywhere in the code to stop execution and get a debugger console
gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
# Adds support for Capybara system testing and selenium driver
gem 'capybara', '~> 2.13'
gem 'selenium-webdriver'
endgroup :development, :test do 這行的意思是，只有在開發和測試環境下才需要安裝的套件。因為我們的 heroku 的環境是 :production，所以我們如果把 gem 'pg', '~> 0.21.0' 寫在這個 group 裡的話，heroku 就還是壞的。
其中~> 0.21.0 表示版本號，一個套件會隨著時間不斷更新，就像 iOS 和 Android 也會一直系統更新一樣。我們可以指定想要安裝的版本。
改完 Gemfile 之後，先關閉網頁伺服器，然後在小黑框輸入 bundle install 安裝新套件完之後再打開網頁伺服器。
再次進行本機測試
正常！
把改動後的程式碼上傳到 heroku
上傳到 heroku 之前要先建立一個 git 版本，之前提到過的上傳三步驟：
git add .
git commit -m "註解"
git push heroku master如果你覺得註解亂寫沒關係的話，我是沒差，你可以直接複製上面三行程式碼到小黑框貼上。不過我就一步步來。
git add .
選擇所有檔案加入這次的版本：
D:\只要有心，人人都可以作卡米狗\ironman>git add .
warning: LF will be replaced by CRLF in Gemfile.
The file will have its original line endings in your working directory.
warning: LF will be replaced by CRLF in Gemfile.lock.
The file will have its original line endings in your working directory.
warning: LF will be replaced by CRLF in config/database.yml.
The file will have its original line endings in your working directory.git commit -m "改用pg"
建立一個版本，我的註解是寫 改用pg 說明我們這次的改動：
D:\只要有心，人人都可以作卡米狗\ironman>git commit -m "改用pg"
[master e6f3871] '改用pg'
3 files changed, 5 insertions(+), 2 deletions(-)
D:\只要有心，人人都可以作卡米狗\ironman>git push heroku master
上傳程式碼到 heroku：
D:\只要有心，人人都可以作卡米狗\ironman>git push heroku master
Counting objects: 3, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 297 bytes | 297.00 KiB/s, done.
Total 3 (delta 2), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Ruby app detected
remote: -----> Compiling Ruby/Rails
remote: -----> Using Ruby version: ruby-2.3.4
remote: ###### WARNING:
remote: Removing `Gemfile.lock` because it was generated on Windows.
remote: Bundler will do a full resolve so native gems are handled properly.
remote: This may result in unexpected gem versions being used in your app.
remote: In rare occasions Bundler may not be able to resolve your dependencies at all.
remote: https://devcenter.heroku.com/articles/bundler-windows-gemfile
remote:
remote: -----> Installing dependencies using bundler 1.15.2
remote: Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4
remote: The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
remote: Fetching gem metadata from https://rubygems.org/..........
remote: Fetching version metadata from https://rubygems.org/..
remote: Fetching dependency metadata from https://rubygems.org/.
remote: Resolving dependencies...
remote: Using rake 12.3.0
remote: Using concurrent-ruby 1.0.5
remote: Using minitest 5.11.1
remote: Using thread_safe 0.3.6
remote: Using builder 3.2.3
remote: Using erubi 1.7.0
remote: Using mini_portile2 2.3.0
remote: Using crass 1.0.3
remote: Using rack 2.0.3
remote: Using nio4r 2.2.0
remote: Using websocket-extensions 0.1.3
remote: Using mini_mime 1.0.0
remote: Using arel 8.0.0
remote: Using bundler 1.15.2
remote: Using coffee-script-source 1.12.2
remote: Using execjs 2.7.0
remote: Using method_source 0.9.0
remote: Using thor 0.20.0
remote: Using ffi 1.9.18
remote: Using multi_json 1.12.2
remote: Fetching pg 0.21.0
remote: Using puma 3.11.0
remote: Using rb-fsevent 0.10.2
remote: Using tilt 2.0.8
remote: Using turbolinks-source 5.0.3
remote: Using tzinfo 1.2.4
remote: Using nokogiri 1.8.1
remote: Using i18n 0.9.1
remote: Using rack-test 0.8.2
remote: Using sprockets 3.7.1
remote: Using websocket-driver 0.6.5
remote: Using mail 2.7.0
remote: Using coffee-script 2.4.1
remote: Using uglifier 4.1.2
remote: Using rb-inotify 0.9.10
remote: Using turbolinks 5.0.1
remote: Using loofah 2.1.1
remote: Using activesupport 5.1.4
remote: Using sass-listen 4.0.0
remote: Using rails-html-sanitizer 1.0.3
remote: Using rails-dom-testing 2.0.3
remote: Using globalid 0.4.1
remote: Using activemodel 5.1.4
remote: Using jbuilder 2.7.0
remote: Using sass 3.5.5
remote: Using actionview 5.1.4
remote: Using activejob 5.1.4
remote: Using activerecord 5.1.4
remote: Using actionpack 5.1.4
remote: Using actioncable 5.1.4
remote: Using actionmailer 5.1.4
remote: Using railties 5.1.4
remote: Using sprockets-rails 3.2.1
remote: Using coffee-rails 4.2.2
remote: Using rails 5.1.4
remote: Using sass-rails 5.0.7
remote: Installing pg 0.21.0 with native extensions
remote: Bundle complete! 13 Gemfile dependencies, 56 gems now installed.
remote: Gems in the groups development and test were not installed.
remote: Bundled gems are installed into ./vendor/bundle.
remote: Bundle completed (11.93s)
remote: Cleaning up the bundler cache.
remote: The latest bundler is 1.16.1, but you are currently running 1.15.2.
remote: To update, run `gem install bundler`
remote: -----> Installing node-v6.11.1-linux-x64
remote: -----> Detecting rake tasks
remote: -----> Preparing app for Rails asset pipeline
remote: Running: rake assets:precompile
remote: Yarn executable was not detected in the system.
remote: Download Yarn at https://yarnpkg.com/en/docs/install
remote: Asset precompilation completed (1.50s)
remote: Cleaning assets
remote: Running: rake assets:clean
remote:
remote: ###### WARNING:
remote: You have not declared a Ruby version in your Gemfile.
remote: To set your Ruby version add this line to your Gemfile:
remote: ruby '2.3.4'
remote: # See https://devcenter.heroku.com/articles/ruby-versions for more information.
remote:
remote: ###### WARNING:
remote: Removing `Gemfile.lock` because it was generated on Windows.
remote: Bundler will do a full resolve so native gems are handled properly.
remote: This may result in unexpected gem versions being used in your app.
remote: In rare occasions Bundler may not be able to resolve your dependencies at all.
remote: https://devcenter.heroku.com/articles/bundler-windows-gemfile
remote:
remote: ###### WARNING:
remote: No Procfile detected, using the default web server.
remote: We recommend explicitly declaring how to boot your server process via a Procfile.
remote: https://devcenter.heroku.com/articles/ruby-default-web-server
remote:
remote: -----> Discovering process types
remote: Procfile declares types -> (none)
remote: Default types for buildpack -> console, rake, web, worker
remote:
remote: -----> Compressing...
remote: Done: 36.7M
remote: -----> Launching...
remote: Released v8
remote: https://people-all-love-kamigo.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/people-all-love-kamigo.git
e6f3871..5ec30ea master -> master
D:\只要有心，人人都可以作卡米狗\ironman>這次看似上傳成功了，從最後面往上看，倒數第 5 行有一個網址：https://people-all-love-kamigo.herokuapp.com/，以及三個 WARNING。
先不管 WARNING，我們複製網址進去看(你的網址會跟我的不同，取決於你之前下 heroku create 指令時輸入的網站名稱)。
Heroku說：「找不到網頁。」
這是因為在我們本機的首頁，其實是不在專案資料夾裡面的，記得一開始修改網頁(第九天：作一個最簡單的 Rails 網站)時，我們是去哪改嗎？是在 C:/Ruby24-x64/lib/ruby/gems/2.4.0/gems/railties-5.1.4/lib/rails/templates/rails/welcome/index.html.erb，而這個檔案並不是在專案資料夾下，所以遠端伺服器沒有這個檔案也是很合邏輯的。
事實上，只有在 config/routes.rb 檔案裏面有寫到的那些路徑才是我們應該測的路徑，所以我們應該連到這裡：https://people-all-love-kamigo.herokuapp.com/kamigo/eat。
吃土啦～
總結
程式碼除錯的流程大致上為：
- 閱讀錯誤訊息
- 修改程式碼
- 測試網站，若失敗則回到第一步
- 發布網站
工程師的日常就是除了一個錯之後看到的不是正常，而是看到下一個錯誤訊息。
要有耐心。
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