DataMapper.setup(:default,'sqlite:///path/to/project.db')
DataMapper.finalize
DataMapper.auto_migrate!
DataMapper.auto_upgrade!

在许多DataMapper Sinatra教程中,我了解到auto_migrate！和auto_upgrade！每次应用程序在生产服务器上加载时,都不应该被调用.但是与此同时,许多示例将这些函数称为sinatra应用程序的主要ruby文件,例如app.rb,无需额外检查.一些例子根本不会调用finalize.到目前为止,我感到困惑,我不知道在生产服务器上该怎么做.

以这个简单的app.rb为例,我有一些问题：

>哪里和什么时候应该最终被调用？
>首次部署应用程序时,生产服务器上没有数据库文件,如何自动创建？还是手动创建project.db文件？
>自从auto_upgrade！包装在：开发块,它不会在生产服务器上调用.当我添加或删除列时,我应该如何升级数据库？

require 'sinatra'
require 'data_mapper'

configure do
  DataMapper.setup :default,"sqlite3://#{Dir.pwd}/project.db"
end

class Book
  include DataMapper::Resource
  property :id,Serial
  property :title,Text

  belongs_to :author
end

class Author
  include DataMapper::Resource
  property :id,Serial
  property :name,Text

  has n,:books
end

configure :development do
  DataMapper.auto_upgrade!
end

get '/:id' do
  @author = Author.get params[:id]
  erb :list_author_and_his_books # The template has nothing to do with this question,ignore it
end

get '/new' do
  # Some code for user to input book or author details
end

get '/create' do
  # Some code to create book or author in db
end

感谢您阅读这篇长篇文章：D