Lua, OOP and nothing more
One day fate brought me to her. At first glance I was blinded and for a long time I could not take my eyes off her. Time passed, but she never ceased to amaze me, sometimes it seemed that I had studied her far and wide, but she turned over all my ideas again. There was no limit to her flexibility, and then I learned that she can also ... OOP!
Somehow, I seriously began to conquer the PLO in lua. And everything that I found on the Internet on this topic was a bunch of code with lots of underscores that did not fit into the elegance of this language. So I decided to look for a simple solution.
After reading a lot of smart books and analyzing several terrible implementations of the PLO, I, bit by bit, collected all the most useful and simple, until I had developed my style of object-oriented programming in lua.
As you can see, everything is very simple. If someone gets confused where to put the period, and where is the colon, the rule is as follows: if we turn to the property, we set the period (object.name), if to the method, we put the colon (object: getName ()).
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Further more interesting.
As it is known, OOP rests on three pillars: inheritance, encapsulation, and polymorphism. We will conduct a "debriefing" in the same manner.
Suppose we need to create a class inherited from the previous one (Person).
Everything works, but personally I do not like this version of inheritance, ugly. Therefore, I simply create the global extended () function:
Now class inheritance looks much more beautiful:
All properties and methods up to this point in our classes were public, but we can also easily create private ones:
Do you see? Everything is almost the same as you used to.
It's still easier.
So what did we do here?
- created the Person class, with two methods: getName () and getName2 (), the first one is protected from overriding;
- created the Woman class and inherited it from the Person class;
- redefined both methods in the Woman class. The first is not overridden;
- got a profit!
By the way, open methods can also be defined outside the class body:
And what if you need to call the method of the base class, which we have overridden? This is also done easily!
The syntax is: ParentClass.Method (self_object, parameters (if any)).
That's all, I sincerely hope that at least someone this article will be useful.
Finally I will give the full code, you can copy it into the IDE and make sure it works.
Somehow, I seriously began to conquer the PLO in lua. And everything that I found on the Internet on this topic was a bunch of code with lots of underscores that did not fit into the elegance of this language. So I decided to look for a simple solution.
After reading a lot of smart books and analyzing several terrible implementations of the PLO, I, bit by bit, collected all the most useful and simple, until I had developed my style of object-oriented programming in lua.
Creating a class and instance
class Person
-- Person= {} -- function Person:new(fName, lName) -- local obj= {} obj.firstName = fName obj.lastName = lName -- function obj:getName() return self.firstName end -- ! setmetatable(obj, self) self.__index = self; return obj end -- vasya = Person:new("", "") -- print(vasya.firstName) --> : -- print(vasya:getName()) --> : As you can see, everything is very simple. If someone gets confused where to put the period, and where is the colon, the rule is as follows: if we turn to the property, we set the period (object.name), if to the method, we put the colon (object: getName ()).
')
Further more interesting.
As it is known, OOP rests on three pillars: inheritance, encapsulation, and polymorphism. We will conduct a "debriefing" in the same manner.
Inheritance
Suppose we need to create a class inherited from the previous one (Person).
class Woman
Woman = {} -- setmetatable(Woman ,{__index = Person}) -- masha = Woman:new("","") print(masha:getName()) --->: Everything works, but personally I do not like this version of inheritance, ugly. Therefore, I simply create the global extended () function:
extended ()
function extended (child, parent) setmetatable(child,{__index = parent}) end Now class inheritance looks much more beautiful:
class Woman
Woman = {}; -- extended(Woman, Person) -- masha = Woman:new("","") print(masha:getName()) --->: Encapsulation
All properties and methods up to this point in our classes were public, but we can also easily create private ones:
class Person
Person = {} function Person:new(name) local private = {} -- private.age = 18 local public = {} -- public.name = name or "" -- "" - -- function public:getAge() return private.age end setmetatable(public,self) self.__index = self; return public end vasya = Person:new() print(vasya.name) --> : print(vasya.age) --> : nil print(vasya:getAge()) --> : 18 Do you see? Everything is almost the same as you used to.
Polymorphism
It's still easier.
polymorphism
Person = {} function Person:new(name) local private = {} private.age = 18 local public = {} public.name = name or "" -- , function public:getName() return "Person protected "..self.name end -- , function Person:getName2() return "Person "..self.name end setmetatable(public,self) self.__index = self; return public end -- , Person Woman = {} extended(Woman, Person) -- -- function Woman:getName() return "Woman protected "..self.name end -- getName2() function Woman:getName2() return "Woman "..self.name end -- masha = Woman:new() print(masha:getName()) --> Person protected print(masha:getName2()) --> Woman So what did we do here?
- created the Person class, with two methods: getName () and getName2 (), the first one is protected from overriding;
- created the Woman class and inherited it from the Person class;
- redefined both methods in the Woman class. The first is not overridden;
- got a profit!
By the way, open methods can also be defined outside the class body:
polymorphism
Person = {} function Person:new(name) local private = {} private.age = 18 local public = {} public.name = name or "" -- , function public:getName() return "Person protected "..self.name end setmetatable(public,self) self.__index = self; return public end -- , function Person:getName2() return "Person "..self.name end And what if you need to call the method of the base class, which we have overridden? This is also done easily!
The syntax is: ParentClass.Method (self_object, parameters (if any)).
class Woman
-- , Person Woman = {} extended(Woman, Person) -- -- setName function Woman:getName2() return "Woman "..self.name end print(masha:getName2()) --> Woman -- print(Person.getName2(masha)) --> Person P.S
That's all, I sincerely hope that at least someone this article will be useful.
Finally I will give the full code, you can copy it into the IDE and make sure it works.
Full code
function extended (child, parent) setmetatable(child,{__index = parent}) end Person = {} function Person:new(name) local private = {} private.age = 18 local public = {} public.name = name or "" -- , function public:getName() return "Person protected "..self.name end -- function Person:getName2() return "Person "..self.name end setmetatable(public,self) self.__index = self; return public end -- , Person Woman = {} extended(Woman, Person) -- -- setName function Woman:getName2() return "Woman "..self.name end masha = Woman:new() print(masha:getName2()) --> Woman -- print(Person.getName2(masha)) --> Person Source: https://habr.com/ru/post/259265/
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