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Rails 初学笔记

Last updated at Posted at 2016-08-04

gem的使用说明

gem -v 告訴你 RubyGems 的版本
gem update --system 升級RubyGems的版本
gem install gem_name 安裝某個套件
gem list 列出安裝的套件
gem update gem_name 更新最新版本
gem update 更新所有你安裝的Gems
gem install -v x.x.x gemname 安裝特定版本
gem uninstall gem_name 反安裝
$ bundle install

可以只輸入bundle就是bundle install了。 每次有修改Gemfile這個檔案,都需要重新執行bundle

# 新增
> event = Event.new
> event.name = "Ruby course"
> event.description = "fooobarrr"
> event.capacity = 20
> event.save # 儲存進資料庫,讀者可以觀察另一個指令視窗
> event.id # 輸出主鍵 1,在 Rails 中的主鍵皆為自動遞增的整數 ID

> event = Event.new( :name => "another ruby course", :capacity => 30)
> event.save
> event.id # 輸出主鍵 2,這是第二筆資料

# 查詢
> event = Event.where( :capacity => 20 ).first
> events = Event.where( ["capacity >= ?", 20 ] ).limit(3).order("id desc")

# 更新
> e = Event.find(1) # 找到主鍵為 1 的資料
> e.name # 輸出 Ruby course
> e.update( :name => 'abc', :is_public => false )

# 刪除
> e.destroy

Migration檔案不需要和Model一一對應,像我們來新增一個Migration檔案來新增一個資料庫欄位,請執行:

$ rails g migration add_status_to_events
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