ruby - 为 Sinatra 生成 JSON

Question

我在将生成的对象的 JSON 表示法传递到我的 Sinatra 应用程序时遇到了问题。我的问题是双重的:

• 我有 2 个使用 Sequel gem 映射到数据库的类。当他们生成 JSON 时，它就可以并正确实现。
• 我有一个名为 registration 的自定义类，它将其中一个类映射到一个附加字段。目标是从中生成 JSON 并将该 JSON 传递给使用 Cucumber 的应用程序(测试目的)

负责处理请求的应用程序代码定义了以下函数:

post '/users' do
  begin
    hash = JSON.parse(self.request.body.read)
    registration = Registration.new.from_json(@request.body.read)
    registration.user.country = Database::Alaplaya.get_country_by_iso_code(registration.user.country.iso_code)
    return 400 unless(registration.is_valid?)
    id = Database::Alaplaya.create_user(registration.user)

    # If the registration failed in our system, return a page 400.
    return 400 if id < 1
end

• 问题 1:我无法使用参数散列。它存在但只是一个空哈希。为什么？
• 问题 2:我无法反序列化类本身生成的 JSON。为什么？

注册类如下所示:

require 'json'

class Registration
  attr_accessor :user, :project_id

  def to_json(*a)
    {
        'json_class'   => self.class.name,
        'data'         => [@user.to_json(*a), @project_id]
    }.to_json(*a)
  end

  def self.json_create(o)
    new(*o['data'])
  end

  # Creates a new instance of the class using the information provided in the
  # hash. If a field is missing in the hash, nil will be assigned to that field
  # instead.
  def initialize(params = {})
    @user = params[:user]
    @project_id = params[:project_id]
  end

  # Returns a string representing the entire Registration.
  def inspect
    "#{@user.inspect} - #{@user.country.inspect} - #{@project_id}"
  end

  # Returns a boolean valid representing whether the Registration instance is
  # considered valid for the API or not. True if the instance is considered
  # valid; otherwise false.
  def is_valid?
    return false if @user.nil? || @project_id.nil?
    return false if !@user.is_a?(User) || !@project_id.is_a?(Fixnum)
    return false if !@user.is_valid?
    true
  end
end

我必须实现正确生成 JSON 输出的方法。当我在控制台中运行它时，会生成以下输出:

irb(main):004:0> r = Registration.new(:user => u, :project_id => 1)
=> new_login - nil - 1
irb(main):005:0> r.to_json
=> "{\"json_class\":\"Registration\",\"data\":[\"{\\\"json_class\\\":\\\"User\\\
",\\\"login\\\":\\\"new_login\\\"}\",1]}"

这对我来说看起来像是有效的 JSON。然而，当我将其发布到应用程序服务器并尝试对其进行解析时，JSON 提示至少需要 2 个八位字节并拒绝反序列化该对象。

Answer 1

如果您使用 Sequel 作为 ORM，请尝试以下操作:

在你的模型中:

class Registration < Sequel::Model
  many_to_one :user
  many_to_one :project
  plugin :json_serializer
end        

服务器:

before do
  @data = JSON.parse(request.body.read) rescue {}
end

post '/users' do
  @registration = Registration.new @data
  if @registration.valid?
    @registration.save 
    @registration.to_json #return a JSON representation of the resource
  else
    status 422 #proper status code for invalid input
    @registration.errors.to_json
  end
end

我认为您的注册过程可能过于复杂了。如果 HTTP 操作是 POST/users 那么为什么不创建一个用户呢？似乎创建一个 registration 过于复杂。除非您的用户已经存在，否则 POST/users 将是不正确的。如果您真正打算做的是将用户添加到项目中，那么您应该 PUT/projects/:project_id/users/:user_id 并且操作看起来像这样:

class User < Sequel::Model
  many_to_many :projects
end
class Project < Sequel::Model
  many_to_many :users
end
#make sure your db schema has a table called users_projects or projects_users

put '/projects/:project_id/users/:user_id' do
  #find the project
  @project = Project.find params[:project_id]
  raise Sinatra::NotFound unless @project
  #find the user
  @user = Project.find params[:project_id]
  raise Sinatra::NotFound unless @user
  #add user to project's users collection
  @project.add_user @user
  #send a new representation of the parent resource back to the client
  #i like to include the child resources as well
  #json might look something like this
  #{ 'name' : 'a project name', 'users' : ['/users/:user_id', '/users/:another_user_id'] }
  @project.to_json
end