List

Let's look closer at this part:

argentina = Reality::Entity('Argentina')

argentina.neighbours
# => #<Reality::List[Uruguay?, Brazil?, Chile?, Paraguay?, Bolivia?]>

Reality::List is just array of entities, with some useful differences. For example, it provides more concise output (compare with argentina.neighbours.to_a on your own). It also provides ability to batch-load all entities in list:

# instead of:
# argentina.neighbours.each(&:load!)
# ...which will be 5 separate requests to Wikipedia and 5 to Wikidata
# ...you can write:
argentina.neighbours.load!
# ...which is 1 request to Wikipedia API and 1 to Wikidata

List is smart enough for providing another List on standard Enumerable methods, like this:

argentina.neighbours.first(2).load!
# => #<Reality::List[Uruguay, Brazil]>

# or even:
argentina.neighbours.load!.map(&:capital)
# => #<Reality::List[Montevideo?, Brasília?, Santiago?, Asunción?, La Paz?]>
argentina.neighbours.load!.map(&:capital).load!
# => #<Reality::List[Montevideo, Brasília, Santiago, Asunción, La Paz]>
argentina.neighbours.map(&:capital).all?(&:loaded?)
# => true

Also, List of loaded entities provides pretty #describe method to quickly look inside:

argentina.neighbours.describe
# -------------------------
# #<Reality::List(5 items)>
# -------------------------
#   keys: adm_divisions (5), area (5), calling_code (5), capital (5), continent (5), coord (5), country (5), created_at (5), currency (5), follows (1), gdp_nominal (5), gdp_ppp (5), head_of_state (5), highest_point (5), iso2_code (5), iso3_code (5), long_name (5), neighbours (5), organizations (5), part_of (5), population (5), tld (5), tz_offset (5)
#  types: country (5)

(OK, not incredibly useful for now, but provides you with some insights on "what's inside".)

Predefined lists

There are some (will be more in future) "default lists" in Reality:

# Root lists
Reality.countries
# => #<Reality::List[Algeria?, Angola?, Benin?, Botswana?, Burkina Faso?, Burundi?, Cameroon?, Cape Verde?, Central African Republic?, Chad?, Comoros?, Republic of the Congo?, Democratic Republic of the Congo?, Djibouti?, Egypt?, Equatorial Guinea?, Eritrea?, Ethiopia?, Gabon?, Gambia?, Ghana?, Guinea?, Guinea-Bissau?, Ivory Coast?, Kenya?, Lesotho?, Liberia?, Libya?, Madagascar?, Malawi?, Mali?, Mauritania?, Mauritius?, Morocco?, Mozambique?, Namibia?, Niger?, Nigeria?, Rwanda?, São Tomé and Príncipe?, Senegal?, Seychelles?, Sierra Leone?, Somalia?, South Africa?, South Sudan?, Sudan?, Swaziland?, Tanzania?, Togo?, Tunisia?, Uganda?, Zambia?, Zimbabwe?, Afghanistan?, Armenia?, Azerbaijan?, Bahrain?, Bangladesh?, Bhutan?, Brunei?, Cambodia?, China?, Cyprus?, East Timor?, Georgia (country)?, India?, Indonesia?, Iran?, Iraq?, Israel?, Japan?, Jordan?, Kazakhstan?, Kuwait?, Kyrgyzstan?, Laos?, Lebanon?, Malaysia?, Maldives?, Mongolia?, Myanmar?, Nepal?, North Korea?, Oman?, Pakistan?, State of Palestine?, Philippines?, Qatar?, Saudi Arabia?, Singapore?, South Korea?, Sri Lanka?, Syria?, Tajikistan?, Thailand?, Turkey?, Turkmenistan?, United Arab Emirates?, Uzbekistan?, Vietnam?, Yemen?, Albania?, Andorra?, Austria?, Belarus?, Belgium?, Bosnia and Herzegovina?, Bulgaria?, Croatia?, Czech Republic?, Denmark?, Estonia?, Finland?, France?, Germany?, Greece?, Hungary?, Iceland?, Republic of Ireland?, Italy?, Latvia?, Liechtenstein?, Lithuania?, Luxembourg?, Republic of Macedonia?, Malta?, Moldova?, Monaco?, Montenegro?, Kingdom of the Netherlands?, Norway?, Poland?, Portugal?, Romania?, Russia?, San Marino?, Serbia?, Slovakia?, Slovenia?, Spain?, Sweden?, Switzerland?, Ukraine?, United Kingdom?, Vatican City?, Antigua and Barbuda?, Bahamas?, Barbados?, Belize?, Canada?, Costa Rica?, Cuba?, Dominica?, Dominican Republic?, El Salvador?, Grenada?, Guatemala?, Haiti?, Honduras?, Jamaica?, Mexico?, Nicaragua?, Panama?, Saint Kitts and Nevis?, Saint Lucia?, Saint Vincent and the Grenadines?, Trinidad and Tobago?, United States?, Argentina?, Bolivia?, Brazil?, Chile?, Colombia?, Ecuador?, Guyana?, Paraguay?, Peru?, Suriname?, Uruguay?, Venezuela?, Australia?, Fiji?, Kiribati?, Marshall Islands?, Federated States of Micronesia?, Nauru?, New Zealand?, Palau?, Papua New Guinea?, Samoa?, Solomon Islands?, Tonga?, Tuvalu?, Vanuatu?]>
Reality.continents
# => #<Reality::List[Asia?, Africa?, North America?, South America?, Antarctica?, Europe?, Australia (continent)?]>

# Navigating through objects:
argentina.cities # fetches "List of cities in Argentina" page and parses it
# => #<Reality::List[Buenos Aires?, "Córdoba, Argentina"?, "Rosario, Santa Fe"?, "Mendoza, Argentina"?, La Plata?, San Miguel de Tucumán?, Mar del Plata?, Salta?, "Santa Fe, Argentina"?, "San Juan, Argentina"?, "Resistencia, Chaco"?, Neuquén?, Santiago del Estero?, Corrientes?, Avellaneda?, Bahía Blanca?, San Salvador de Jujuy?, Quilmes?, Lanús?, Comodoro Rivadavia?, "Concordia, Entre Ríos"?]>

Though, there are some funny quirks with lists (still thinking of it).

Next: simple helper value objects.