从超类型对象创建红宝石对象

Question

I am using the Selenium Webdriver libraries in Ruby. A typical piece of code looks like this:

require 'rubygems'
require 'selenium-webdriver'
driver = Selenium::WebDriver.for :firefox 
# driver is an instance of Selenium::WebDriver::Driver

url = 'http://www.google.com/'
wait = Selenium::WebDriver::Wait.new(:timeout => 10)
driver.get(url)
wait.until { driver.title.start_with? "Google" }

I would like to create a subclass of Selenium::WebDriver::Driver called Selenium::WebDriver::Driver::MyClass that will contain some new methods and instance variables.

As the above code illustrates, the way that instances of Selenium::WebDriver::Driver are created is with Selenium::WebDriver.for .

Without wholesale copying of code, how can I create a version of Selenium::WebDriver.for that does the same thing as Selenium::WebDriver.for but creates instances of Selenium::WebDriver::Driver::MyClass ?

Answer 1

Why not just override the Selenium::WebDriver.for ? let me show you that my an example

# selenium code
module Selenium
  class WebDriver
    def self.for
      puts "creating oldclass"
    end
  end
end

# your code
class Selenium::WebDriver
  def self.for
    puts "creating myclass"
  end
end

Selenium::WebDriver.for

output:

creating myclass

Safe alternative is to derive class from Selenium::WebDriver and use that in your code, or to the extreme you can just open Driver class and add your behavior to it.

Answer 2

Check the source code . Selenium::WebDriver.for simply delegate the method call to Selenium::WebDriver::Driver.for .

If you don't have listener attached, you can simple create your own bridge MyClass::Bridge.new and then pass that to Selenium::WebDriver::Driver.new .

If you insist override the for method, here is some code snippet that might help.

module Selenium
  module WebDriver
    class Driver
      class << self
        alias_method :old_for, :for
        def for(browser, opts = {})
          if browser == :myclass
            # create your MyClass::Bridge instance and pass that to new()
          else
            old_for(browser, opts)
          end
        end
      end
    end
  end
end

Answer 3

If you just want to define some extra methods on your driver, you do not need to override WebDriver.for.

The following worked well for me:

First, in file customdriver.rb

require 'selenium-webdriver'
class CustomDriver < Selenium::WebDriver::Driver 
  #a custom method..
  def click_on (_id)
    element = find_element :id => _id
    element.click
  end 
  #add other custom methods here
  #....
end

Then, in file main.rb

require-relative 'customdriver'
driver = CustomDriver.for :chrome
driver.click_on("buttonID")

Regards,