Add a template of trigger.

spec/test-triggers.cr

@@ -0,0 +1,58 @@
+require "spec"
+require "./db-cars.cr"
+
+class DODB::Trigger::Virtual(V) < DODB::Trigger(V)
+	# Indexes a value, used for **internal operations**.
+	def index(key : String, value : V)
+		puts "index: key #{key}, value #{value}"
+	end
+
+	# Removes the index of a value, used for **internal operations**.
+	def deindex(key : String, value : V)
+		puts "deindex: key #{key}, value #{value}"
+	end
+
+	# Verifies whether a new value will create a collision with the index of
+	# currently stored value, used for **internal operations**.
+	def check!(key : String, value : V, old_value : V?)
+		puts "check!: key #{key}, value #{value}, old_value #{old_value}"
+		false
+	end
+
+	# Name of the index, such as *id* or *color* for example.
+	# This is an arbitrary value, mostly to create the index directory.
+	def name : String
+		name = "some name"
+		puts "name: #{name}"
+		name
+	end
+
+	# Directory where the values will be written.
+	def trigger_directory : String
+		dir = "something"
+		puts "trigger directory: #{dir}"
+		dir
+	end
+
+	# Removes all the index entries, removes the `#trigger_directory` by default.
+	def nuke_trigger
+		puts "nuke trigger"
+	end
+end
+
+car0 = Car.new "Corvet-0", "red", [] of String
+car1 = Car.new "Corvet-1", "red", [] of String
+car2 = Car.new "Corvet-2", "red", [] of String
+car3 = Car.new "Corvet-3", "red", [] of String
+
+db = SPECDB::Common(Car).new "test-triggers", 2
+db.triggers << DODB::Trigger::Virtual(Car).new
+db << car0
+db.delete 0
+db << car0
+db << car1
+carm = car1
+carm.name = "modified"
+db << carm
+db << car2
+db << car3