OpenEuphoria

Classless class-oriented programming

• Posted by jmduro Oct 24, 2021
• 1103 views

In a previous article I showed a preprocessor to allow class-like programming. There are many other ways to do the job.

Here is one which could even be used with previous preprocessor.

Here is the library (classes.e):

namespace classes 
 
include std/convert.e 
 
-- INTERNAL CONSTANTS 
constant CLASS_NAME   =1, CLASS_PROPERTY=2,   CLASS_METHOD=3 
constant PROPERTY_NAME=1, PROPERTY_VALUE=2 
constant METHOD_NAME  =1, METHOD_ROUTINE_ID=2 
constant CLASS_ID     =1, ENTITY_VALUES=2 
 
-- INTERNAL VARIABLES 
public sequence classes = {}, entities = {} 
 
-- INTERNAL FUNCTIONS 
procedure error_message(sequence msg) 
  puts(2, "Error: " & msg & "\n")  
  abort(1)  
end procedure 
 
-- GLOBAL CLASS FUNCTIONS 
 
-- define a ClassName 
-- given the ClassName Name returns the ClassName ID 
public function class(sequence className) 
  classes = append(classes, {className, {}, {}}) 
  return length(classes) 
end function 
 
-- define a ClassName property 
public procedure addProperty(integer classID, sequence propertyName, object defaultValue) 
  if classID > 0 then 
    classes[classID][CLASS_PROPERTY] = append(classes[classID][CLASS_PROPERTY], {propertyName, defaultValue}) 
  else 
    error_message(sprintf("addProperty(%d, \"%s\", %s): no ClassName parameter\n", 
                      {classID, propertyName, to_string(defaultValue)})) 
  end if 
end procedure 
 
-- define a ClassName method 
public procedure addMethod(integer classID, sequence methodName, integer routineId) 
  if classID > 0 then 
    classes[classID][CLASS_METHOD] = append(classes[classID][CLASS_METHOD], {methodName, routineId}) 
  else 
    error_message(sprintf("addMethod(%d, \"%s\", %d): no ClassName parameter\n", 
                      {classID, methodName, routineId})) 
  end if 
end procedure 
 
-- get the class name of a class ID 
public function findClass(sequence name) 
  for i = 1 to length(classes) do 
    if equal(name, classes[i][CLASS_NAME]) then return i end if 
  end for 
  return 0 
end function 
 
-- find property 
public function findProperty(integer classID, sequence property) 
  for i = 1 to length(classes[classID][CLASS_PROPERTY]) do 
    if equal(property, classes[classID][CLASS_PROPERTY][i][PROPERTY_NAME]) then 
      return i 
    end if 
  end for 
  return 0 
end function 
 
-- find method routine_id 
public function findMethod(integer classID, sequence method) 
  for i = 1 to length(classes[classID][CLASS_METHOD]) do 
    if equal(method, classes[classID][CLASS_METHOD][i][METHOD_NAME]) then 
      return classes[classID][CLASS_METHOD][i][METHOD_ROUTINE_ID] 
    end if 
  end for 
  return 0 
end function 
 
-- GLOBAL ENTITY FUNCTIONS 
 
-- create an Entity of the class ClassName 
public function new(integer classID) 
  sequence class = classes[classID] 
  sequence values =  {} 
  for i = 1 to length(class[CLASS_PROPERTY]) do 
    values = append(values, class[CLASS_PROPERTY][i][PROPERTY_VALUE]) 
  end for 
  entities = append(entities, {classID, values}) 
  return length(entities) 
end function 
 
-- get entity class ID 
public function getClassID(integer entityID) 
  return entities[entityID][CLASS_ID] 
end function 
 
-- get property value 
public function getProperty(integer entityID, sequence property, object defaultValue=0) 
  integer classID = entities[entityID][CLASS_ID] 
  integer propertyID = findProperty(classID, property) 
  if propertyID then 
    return entities[entityID][ENTITY_VALUES][propertyID] 
  end if 
  return defaultValue 
end function 
 
-- set property value 
public procedure setProperty(integer entityID, sequence property, object val) 
  integer classID = entities[entityID][CLASS_ID] 
  integer propertyID = findProperty(classID, property) 
  if propertyID then 
    entities[entityID][ENTITY_VALUES][propertyID] = val 
  end if 
end procedure 
 
-- call a method (function) within an Entity 
public function callMethod(integer entityID, sequence method, object methodParams= {}) 
  integer classID = entities[entityID][CLASS_ID] 
  integer methodID = findMethod(classID, method) 
  if methodID then 
    return call_func(methodID, {entityID, methodParams}) 
  end if 
  return -1 
end function