Rails Development Details (i)

Common commands

Rails new New_app 
     
cd New_app
     
rake db:create
     
Rails server 
     
rails generate controller Blog action1 action2< C5/>rails Generate scaffold Product title:string Description:text

Rails Generate model Comment commenter:string body:text post:references

Rake db:migrate
     
rake db:rollback
     
Rails test:units
     
Rails Console

Conventions

There are a lot of conventions in rails, and it's these conventions that save us time, and let us clearly understand the structure of the project and the location of the file.

Table Name Conventions

The table name defaults to use the plural form of model, lowercase. For example: Model is sheep, the default table name is Sheeps, if we want to customize some other names, or based on an existing data table for development, can not modify the name of the datasheet, then we can use the following code to specify the name of the table.

Class Sheep < activerecord::base 
     
  Self.table_name = "Sheep"
     
End

Conventions for table primary keys

Default primary Key name ID, integer, self-increasing. The name in the datasheet is the ID, which is also accessed by the. ID in the model. If you want to specify a different name, you can do so by using the following code.

Class Legacybook < activerecord::base 
     
  Self.primary_ke = "ISBN"
     
end

After the above modification, the data table's primary key column name becomes ISBN, also through the model. ISBN to access. One exception, however, is to assign a value to a primary key or to use an ID to assign it.

Book = legacyboo.new
book.id = "1-214-985"
Book.title = "Programming in Ruby"

In addition to assigning a value to a primary key requires an ID, the specified column name is used at other times.

Model of the relationship

There are three kinds of table relationships:

One-to-one

One-to-many

Many-to-many

The declarations used in model are: Has_one, Has_many, Belongs_to, Has_and_belongs_to_many.

One-to-one

Class Order < ActiveRecord::Base 
  Has_one:invoice 
End 
     
class Invoice < ActiveRecord::Base 
  Belongs_to:order End 

An order has an invoice header, a one-to-one relationship.

One thing is important: a table with a foreign key must have a belongs_to declaration.

One-to-many

Class Order < ActiveRecord::Base 
  Has_many:line_items 
End 
     
class LineItem < ActiveRecord::Base 
  Belongs_to:order End 

An order will have a lot of item and a one-to-many relationship.

Many-to-many

Class Product < activerecord::base 
  has_and_belongs_to_many:categories 
End 
     
class Category < ActiveRecord::Base 
  has_and_belongs_to_many:p roducts 
End

A product belongs to multiple catalogs, and a directory contains multiple products and many-to-many relationships. In addition to the Products table and Categories table, there will be an intermediate table categories_products (category_id, product_id) to store the relationship.

We can also define the relational tables ourselves, and we can store some other information, some information about the relationship. In fact, the relationship between many and many to separate, to become two a one-to-many relationship, so it is better to understand.

SOURCE http://virusswb.blog.51cto.com/115214/1016250