使用Sinatra和Datamapper的虛擬屬性

Question

我正在將Rails應用程序轉換爲Sinatra。該應用程序依賴於支持虛擬屬性的ActiveRecord，但是，我正努力在DataMapper中尋找類似的支持。

在Rails中，我使用了一種算法來根據分數生成分數和排序記錄。虛擬屬性是這一過程的核心。有誰知道如何在Sinatra/DM中複製這個功能？

我接受任何解決方法。重構可能會稍後，因爲我現在只對功能感興趣。

理論上的解決方案將工作是這樣的：

require 'sinatra' 
require 'data_mapper' 
require 'haml' 

DataMapper::setup(:default,"sqlite3://#{Dir.pwd}/example.db") 

class Link 
    include DataMapper::Resource 
    property :id, Serial 
    property :title, Text 
    property :url, String 
    property :points, Integer, :default => 0 
    property :created_at, Time 

    attr_accessor :score 

    def calculate_score 
    time_elapsed = (Time.now - self.created_at)/3600 
    self.score = (self.points-1)/(time_elapsed+2)**1.8 
    end 
end 

DataMapper.finalize.auto_upgrade! 

get '/hot' do 
    @links = Link.all :order => :score.desc 
    haml :index 
end 

Answer 1

我沒有使用DataMapper的，但是我覺得這個代碼將會給你需要的功能：變更內容包括，新的類方法上鍊接all_sorted_desc和呼叫在'get'請求中

require 'sinatra' 
require 'data_mapper' 
require 'haml' 

DataMapper::setup(:default,"sqlite3://#{Dir.pwd}/example.db") 

class Link 
    include DataMapper::Resource 
    property :id, Serial 
    property :title, Text 
    property :url, String 
    property :points, Integer, :default => 0 
    property :created_at, Time 

    attr_accessor :score 

    def calculate_score 
    time_elapsed = (Time.now - self.created_at)/3600 
    self.score = (self.points-1)/(time_elapsed+2)**1.8 
    end 

    def self.all_sorted_desc 
    self.all.each { |item| item.calculate_score }.sort { |a,b| a.score <=> b.score }.reverse 
    end 
end 

DataMapper.finalize.auto_upgrade! 

get '/hot' do 
    @links = Link.all_sorted_desc 
    haml :index 
end