the rails philosophy includes two major guiding principles:
Don't repeat yourself: DRY is a principle of software development which states that "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system". By not writing the same information over and over again. our code is more maintainable, more extensible, and less buggy.
Convention over Configuration: Rails has opinions about the best way to do many things in a web application, and defaults to this set of conventions, rather than require that you specify every minutiae through endless configuration files.
通过rubyonrails-guides,建立一个博客（全英文阅读）
命令：
rails new -h //看帮助help.
link_to //method,Rail's built-in view helpers.
**
<%= link_to("My Blog", controller: "articles")%> //当你链接到一个行为，而不在同一个controller的时候，你需要指定:controller option.
注释：⚠️ guide里有关于调用error_explanation的使用方法。如：pluralize(), @name,errors.full_messages.
❌：
1.undefined method `each' for nil:NilClass
分析：问题出在nilclass,each指向的class是空的。看一下传入的实例变量名字是不是写错了。
单词：
distinction:(区别)
trm/ (temporary:) 临时文件，缓存和pid
execute(kill sb/do sth/ferform an action)
malicious [mə'lɪʃəs] (very unkind and cruel, and deliberately behaving in a way that is likely to upset or hurt someone )
proceed:(verb, continue to do one thing)
process:(n,过程，进程，v,加工处理食品，数据等)
retrieve [rɪ'triːv]: to find sth and bring it back formal. to get back information that has been stored in the memory of a computer technical.检索。
new.html.erb 文件中。文件的扩展名很重要：第一个扩展名是模板格式，第二个扩展名是模板处理器。这个模板的格式只能是 html，模板处理器只能是 erb、builder和 coffee 中的一个。:erb 是最常用的 HTML 模板处理器，:builder 是 XML 模板处理器，:coffee 模板处理器用 CoffeeScript 创建 JavaScript 模板。因为我们要创建 HTML 表单，所以应该使用能够在 HTML 中嵌入 Ruby 的 ERB 语言。
5.6 saving data in the controller
Class names in Ruby must begin with a capital letter.
render plain: params[:article].inspect 返回参数key的值并显示在屏幕上。
5.10 Adding Some Validation
redirect_to 和 render的一个区别
redirect_to :tell the browser to issue another request.（因此效能较低）
render: is done within the same request as the form submission(submit提交)
5.11 Updating Articles
@article.update(article_params) 更新全部,也可以更新部分内容，如下：
@article.update(text:"A new title")
formhelper activeview::helpers
http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-form_for-label-Resource-oriented+style
t.integer :supplier_id 更明确地表明了外键的名称。在目前的 Rails 版本中，可以抽象实现的细节，使用 t.references :supplier 代替。
foreign_key 用于定义给关联的索引换一个名字
@comment = @article.comments.create //create相当于new and save.
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Arial; color: #3d3d3d; -webkit-text-stroke: #3d3d3d}
span.s1 {font-kerning: none}
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Arial; color: #666666; -webkit-text-stroke: #666666}
span.s1 {font-kerning: none}
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Arial; color: #646464; -webkit-text-stroke: #646464}
span.s1 {font-kerning: none}