Ruby on Rails，创建最简单的视图/控制器单元Hello World

在Ruby
on Rails，创建一个最简单的站点中我们通过rails new simple_site命令创建了一个web应用骨架。笔墨纸砚都准备好了，该是时候写出第一个Hello World啦~！

Rails明确的按照MVC结构组织内容，回想一下MVC结构的简单知识。Browser（浏览器）向Controller（控制器）发出交互请求；Controller对请求做出分发处理调用Model（模型）进行业务或者数据运算；Controller将Model运算的结果推送给View（视图）使其在Browser中绘制显示。作为Hello World来说，建立一个从Browser到Controller再到View的例子既简单有很能说明问题。也就是说这个例子中不涉及与模型及数据库的任何操作，只是由Controller根据Browser发来的请求进行相应，并将相应交给View显示在Browser上。



进入应用目录simple_site，使用生成命令rails generate。这个命令负责在当前目录按照参数要求生成目录结构及代码。不带任何参数的命令会显示提示信息。

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E:\greensoft\RailsInstaller\Sites\simple_site>rails generate

Usage: rails generate GENERATOR [args] [options]



General options:

-h, [--help] # Print generator's options and usage

-p, [--pretend] # Run but do not make any changes

-f, [--force] # Overwrite files that already exist

-s, [--skip] # Skip files that already exist

-q, [--quiet] # Suppress status output



Please choose a generator below.



Rails:

assets

controller

generator

helper

integration_test

mailer

migration

model

observer

performance_test

resource

scaffold

scaffold_controller

session_migration

task



Coffee:

coffee:assets



Jquery:

jquery:install



Js:

js:assets

我们需要创建Controller和View，使用rails generate controller命令。不带任何参数的命令会对创建controller的使用方式进行提示，应该静下心来读一读。其中最有用的部分是说，以CamelCase（大写字母开头分割单词）或者under_scored（下划线分割单词）的方式命名Controller，将View名称列表以参数的方式给出。后面还举了一个很典型的例子。

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E:\greensoft\RailsInstaller\Sites\simple_site>rails generate controller

Usage:

rails generate controller NAME [action action] [options]



Options:

[--skip-namespace] # Skip namespace (affects only isolated applications)

[--old-style-hash] # Force using old style hash (:foo => 'bar') on Ruby >= 1.9

-e, [--template-engine=NAME] # Template engine to be invoked

# Default: erb

-t, [--test-framework=NAME] # Test framework to be invoked

# Default: test_unit

[--helper] # Indicates when to generate helper

# Default: true

[--assets] # Indicates when to generate assets

# Default: true



Runtime options:

-f, [--force] # Overwrite files that already exist

-p, [--pretend] # Run but do not make any changes

-q, [--quiet] # Supress status output

-s, [--skip] # Skip files that already exist



Description:

Stubs out a new controller and its views. Pass the controller name, either

CamelCased or under_scored, and a list of views as arguments.



To create a controller within a module, specify the controller name as a

path like 'parent_module/controller_name'.



This generates a controller class in app/controllers and invokes helper,

template engine and test framework generators.



Example:

`rails generate controller CreditCard open debit credit close`



Credit card controller with URLs like /credit_card/debit.

Controller: app/controllers/credit_card_controller.rb

Functional Test: test/functional/credit_card_controller_test.rb

Views: app/views/credit_card/debit.html.erb [...]

Helper: app/helpers/credit_card_helper.rb

我们要创建一个名为demo的Controller，指向名为index的View。在这里可以使用g来代替generate，就像s代替service一样。回显信息告诉我们，rails为我们在app/controller目录中创建了一个名为demo_controller的Controller。app/views/目录中创建了一个名为demo的目录，目录中的index.html.erb对应View。

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E:\greensoft\RailsInstaller\Sites\simple_site>rails g controller demo index

create app/controllers/demo_controller.rb

route get "demo/index"

invoke erb

create app/views/demo

create app/views/demo/index.html.erb

invoke test_unit

create test/functional/demo_controller_test.rb

invoke helper

create app/helpers/demo_helper.rb

invoke test_unit

create test/unit/helpers/demo_helper_test.rb

invoke assets

invoke coffee

create app/assets/javascripts/demo.js.coffee

invoke scss

create app/assets/stylesheets/demo.css.scss

controller目录中名为demo的Controller里有一个名为index的方法，在在这里应该叫做action。这个叫index的action，对应views目录中名为index.html.erb的View。

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class DemoController < ApplicationController

def index

end

end

修改一下页面内容

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<h1>Demo#index</h1>

<p>Hello World!</p>

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<p>Find me in app/views/demo/index.html.erb</p>

代码编写完毕，启动web服务器。在浏览器地址栏中输入：localhost:3000/demo/index。里程碑！