Ruby: how to use constant name instead of its value

Question

I am new to automating tests using Ruby (in combination with Selenium) and struggling to use the name of a constant instead of its value in my test_steps.rb.

I'm using the 3 files below:

LoginPage.rb:

class LoginPage < Base

  FIELDS = {
    'Username' => '//form[@id="login"]//input[@name="j_username"]',
  }

Base.rb:

def fill_field(field, value)
  find(:xpath, field, wait: 15).set(value)
  #logger("Filling field with xpath '" + field + "' with value '" +
             value + "'.") > this works fine but prints the xpath

  p "field: " + field
  log = field.scan(/\w+(?:'\w+)*/).last
  logger("Filling field '" + log + "' with value '" + value + "'.")

test_steps.rb:

And(/^logs in as user "([^"]*)"$/) do |userName|
  $login_name = search_excel('testdata/accounts.xlsx', userName, 1)
  @pg.fill_field(LoginPage::FIELDS['Username'], $login_name)

When executing the scenario I see this in my command prompt:

Given a user is on the oCRM login page # features/step_definitions/test_steps.rb:13
"field: //form[@id=\"login\"]//input[@name=\"j_username\"]"
28/12/2016 13:03:50 Filling field 'j_username' with value 'D0X02703'.

Note that the line in Base.rb prints the value for the constant matching "field"

'//form[@id="login"]//input[@name="j_username"]'

I would like it to print the constant itself: "LoginPage::FIELDS['Username']". The target is to print this in my logging:

"Filling field 'Username' with value 'DOX02703'."

I've tried printing "field.name", "field.value" and played around with local_variables, but no success yet. Help would be very welcome!

Also tried the other way around with definition below but ofcourse then it won't pick up the constant value and look for xpath "LoginPage::FIELDS['Username']":

  def fill_fields(page, type, field, value)
            find(:xpath, page + "::" + type + "['" + field + "']", wait: 15).set(value)

Answer 1

Constants aren't objects in Ruby. Since you can only pass objects as arguments, and only call methods on objects (and objects are the only values, and method calls are the only way to do something), it is simply not possible to pass a constant as an argument or ask it for its name.

The only thing you can do is pass the name of the constant as an argument instead of or in addition to the object the constant points to.

Answer 2

You could use a String with const_get :

class LoginPage # <Base
  FIELDS = {
    'Username' => '//form[@id="login"]//input[@name="j_username"]',
  }
end

def get_constant_from_string(param)
  puts "Parameter is #{param}"
  Object.const_get(param) if param.is_a?(String)
end

get_constant_from_string(LoginPage::FIELDS)
# Parameter is {"Username"=>"//form[@id=\"login\"]//input[@name=\"j_username\"]"}
# method returns nil

puts get_constant_from_string("LoginPage::FIELDS")['Username']
# Parameter is LoginPage::FIELDS
# //form[@id="login"]//input[@name="j_username"]

Answer 3

Essentially there is no difference between calling

@pg.fill_field(LoginPage::FIELDS['Username'], $login_name)

and

username = LoginPage::FIELDS['Username']
@pg.fill_field(username, $login_name)

it's just that the first one doesn't mention the temporary variable. Either way the only thing passed through to the method is the value associated with the 'Username' key in the hash. Looking at your class structure it seems like you have a number of 'Page' classes that inherit from base, and you're expecting fill_field to use the FIELDS constant from the class that inherited it. In that case you probably want

def fill_field(field, value)
  find(:xpath, self.class::FIELDS[field], wait: 15).set(value)

  logger("Filling field '" + field + "' with value '" + value + "'.")
end

and calling it as

@pg.fill_field('Username', $login_name)

Answer 4

Working solution based on Thomas Walpole's comment:

Base.rb:

def find_field(field)
    @fieldToFill = find(:xpath, self.class::FIELDS[field], wait: 15)
end

def set_value(value)
    @fieldToFill.set(value)
end

def fill_field_log(field, value)
    logger("Filling field '" + field + "' with value '" + value + "'.")           
end

LoginPage.rb:

def fill_field(field, value)
    find_field(field)
    set_value(value)
    fill_field_log(field, value)
end

test_steps.rb:

Given(/^a user is on the login page$/) do
    @pg = Base.new
    @lp = LoginPage.new
    @pg.visit_loginpage
end

And(/^logs in as user "([^"]*)"$/) do |userName|
    $login_name = search_excel('testdata/accounts.xlsx', userName, 1)
    login_password = search_excel('testdata/accounts.xlsx', userName, 2)

    @lp.fill_field('Username', $login_name)
    @lp.fill_field('Password', login_password)