Group items tagged

view templates are written in a language called ERB (Embedded Ruby) which is converted by the request cycle in Rails before being sent to the user.

Each action's purpose is to collect information to provide it to a view.

A view's purpose is to display this information in a human readable format.

routing file which holds entries in a special DSL (domain-specific language) that tells Rails how to connect incoming requests to controllers and actions.

You can create, read, update and destroy items for a resource and these operations are referred to as CRUD operations

A controller is simply a class that is defined to inherit from ApplicationController.

If not found, then it will attempt to load a template called application/new. It looks for one here because the PostsController inherits from ApplicationController

:formats specifies the format of template to be served in response. The default format is :html, and so Rails is looking for an HTML template.

:handlers, is telling us what template handlers could be used to render our template.

When you call form_for, you pass it an identifying object for this form. In this case, it's the symbol :post. This tells the form_for helper what this form is for.

that the action attribute for the form is pointing at /posts/new

When a form is submitted, the fields of the form are sent to Rails as parameters.

parameters can then be referenced inside the controller actions, typically to perform a particular task

params method is the object which represents the parameters (or fields) coming in from the form.

Active Record is smart enough to automatically map column names to model attributes,

Rails uses rake commands to run migrations, and it's possible to undo a migration after it's been applied to your database

every Rails model can be initialized with its respective attributes, which are automatically mapped to the respective database columns.

migration creates a method named change which will be called when you run this migration.

The action defined in this method is also reversible, which means Rails knows how to reverse the change made by this migration, in case you want to reverse it later

Migration filenames include a timestamp to ensure that they're processed in the order that they were created.

@post.save returns a boolean indicating whether the model was saved or not.

prevents an attacker from setting the model's attributes by manipulating the hash passed to the model.

If you want to link to an action in the same controller, you don't need to specify the :controller option, as Rails will use the current controller by default.

inherits from ActiveRecord::Base

Rails includes methods to help you validate the data that you send to models

Rails can validate a variety of conditions in a model, including the presence or uniqueness of columns, their format, and the existence of associated objects.

redirect_to will tell the browser to issue another request.

rendering is done within the same request as the form submission

Each request for a comment has to keep track of the post to which the comment is attached, thus the initial call to the find method of the Post model to get the post in question.

pluralize is a rails helper that takes a number and a string as its arguments. If the number is greater than one, the string will be automatically pluralized.

The render method is used so that the @post object is passed back to the new template when it is rendered.

it accepts a hash containing the attributes that you want to update.

field_with_errors. You can define a css rule to make them standout

belongs_to :post, which sets up an Active Record association

creates comments as a nested resource within posts

call destroy on Active Record objects when you want to delete them from the database.

Rails allows you to use the dependent option of an association to achieve this.

store all external data as UTF-8

you're better off ensuring that all external data is UTF-8

use UTF-8 as the internal storage of your database

Rails defaults to converting data from your database into UTF-8 at the boundary.

:patch

By default forms built with the form_for helper are sent via POST

The :method and :'data-confirm' options are used as HTML5 attributes so that when the link is clicked, Rails will first show a confirm dialog to the user, and then submit the link with method delete. This is done via the JavaScript file jquery_ujs which is automatically included into your application's layout (app/views/layouts/application.html.erb) when you generated the application.

Without this file, the confirmation dialog box wouldn't appear.

just defines the partial template we want to render

As the render method iterates over the @post.comments collection, it assigns each comment to

use the authentication system

require and permit

the method is often made private to make sure it can't be called outside its intended context.

存取資料庫是一種相對很慢的I/O的操作：每一條SQL query都得耗上時間、執行回傳的結果也會被轉成ActiveRecord物件全部放進記憶體

如果需要撈出全部的資料做處理，強烈建議最好不要用all方法，因為這樣會把全部的資料一次放進記憶體中，如果資料有成千上萬筆的話，效能就墜毀了。

.find_each( :batch_size => 100 )

.find_in_batches( :batch_size => 100 )

在Transaction交易範圍內的SQL效能會加快，因為最後只需要COMMIT一次即可

Elasticsearch全文搜尋引擎和elasticsearch-rails gem

QueryReviewer這個套件透過SQL EXPLAIN分析SQL query的效率

必要時可以採用逆正規化的設計。犧牲空間，增加修改的麻煩，但是讓讀取這事件變得更快更簡單。

將成本轉嫁到寫入，而最佳化了讀取時間

在效能還沒有造成問題前，就為了優化效能而修改程式和架構，只會讓程式更混亂不好維護

當效能還不會造成問題時，程式的維護性比考慮效能重要

會拖慢整體效能的程式，只佔全部程式的一小部分而已，所以我們只最佳化會造成問題的程式。

善用分析工具找效能瓶頸，最佳化前需要測量，最佳化後也要測量比較。

rack-mini-profiler在頁面的左上角顯示花了多少時間，並且提供報表，推薦安裝

如果是不需要權限控管的靜態檔案，可以直接放在public目錄下讓使用者下載。

Web伺服器得先安裝好x_sendfile功能

如果要讓你的Assets例如CSS, JavaScript, Images也讓使用者透過CDN下載，只要修改config/environments/production.rb的config.action_controller.asset_host為CDN網址即可。

有時候「執行速度較快」的程式碼不代表好維護、好除錯的程式碼

Ruby不是萬能，有時候直接呼叫外部程式是最快的作法

can overwrite the default label by passing it to the input method

configure the html of any of them

disable labels, hints or error

add a hint, an error, or even a placeholder

add an inline label

pass any html attribute straight to the input, by using the :input_html option

use the :defaults option in simple_form_fo

Simple Form generates a wrapper div around your label and input by default, you can pass any html attribute to that wrapper as well using the :wrapper_html option,

By default all inputs are required

the required property of any input can be overwritten

lets you overwrite the default input type it creates

can also render boolean attributes using as: :select to show a dropdown.

give the :disabled option to Simple Form, and it'll automatically mark the wrapper as disabled with a CSS class

Any extra option passed to these methods will be rendered as html option.

use label, hint, input_field, error and full_error helpers

to strip away all the div wrappers around the <input> field

is to use f.input_field

changing boolean_style from default value :nested to :inline

overriding the :collection option

Collections can be arrays or ranges, and when a :collection is given the :select input will be rendered by default

label_method

value_method

Both of these options also accept lambda/procs

define a to_label method on your model as Simple Form will search for and use :to_label as a :label_method first if it is found

create grouped collection selects, that will use the html optgroup tags

Grouped collection inputs accept the same :label_method and :value_method options

group_method

group_label_method

configured with a default value to be used on the site through the SimpleForm.country_priority and SimpleForm.time_zone_priority helpers.

association

association

render a :select input for choosing the :company, and another :select input with :multiple option for the :roles

all options available to :select, :radio_buttons and :check_boxes are also available to association

f.input

f.select

create a <button> element

simple_fields_for

Creates a collection of radio inputs with labels associated

Creates a collection of checkboxes with labels associated

collection_radio_buttons

collection_check_boxes

associations in your model

Role.all

the html element you will get for each attribute according to its database definition

redefine existing Simple Form inputs by creating a new class with the same name

Simple Form uses all power of I18n API to lookup labels, hints, prompts and placeholders

specify defaults for all models under the 'defaults' key

Simple Form will always look for a default attribute translation under the "defaults" key if no specific is found inside the model key

Simple Form will fallback to default human_attribute_name from Rails when no other translation is found for labels.

Simple Form will only do the lookup for options if you give a collection composed of symbols only.

"Add %{model}"

translations for labels, hints and placeholders for a namespaced model, e.g. Admin::User, should be placed under admin_user, not under admin/user

configure how your components will be rendered using the wrappers API

optional

unless_blank

By default, Simple Form will generate input field types and attributes that are supported in HTML5

The HTML5 extensions include the new field types such as email, number, search, url, tel, and the new attributes such as required, autofocus, maxlength, min, max, step.

If you want to have all other HTML 5 features, such as the new field types, you can disable only the browser validation

add novalidate to a specific form by setting the option on the form itself

the Simple Form configuration file

passing the html5 option

as: :date, html5: true