Object oriented programming, LUA help please!?
This script is in my module(s):
Person = {}
Person.__index = Person
Person.martialArts = {}
function Person.new(name, age, ethnicity)
local newPerson = {}
setmetatable(newPerson,Person)
Person.Name = name
Person.Age = age
Person.Ethnicity = ethnicity
return newPerson
end
-- This is the area that is of problem, concern:
function Person.martialArts.new(style)
local newMartialArts = {}
setmetatable(newMartialArts,Person.martialArts)
style = {}
table.insert(Person.martialArts,style)
return newMartialArts
end
-- This area!
function Person:Swim()
print(self.Name.. " is swimming!")
end
return Person
See where I commented? This is the local script where I'm using this script/code:
Person = require(game.ReplicatedStorage.OOP)
local John = Person.new("John", "Young", "Human")
John.martialArts.new("Karate")
print(John.martialArts.Karate)
I'm trying to have it create a table called "Karate" inside martialArts for this particular person. But it won't create it and when it goes to print, the print says "nil." I don't know what I'm doing wrong.
For instance if I do John.martialArts.new("Karate") it should create the table "Karate" inside martialArts for John.
However, when doing print(John.martialArts.Karate), I simply get nil (whereas I should get an empty table value). Help?
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1 answer
This is not how object oriented programming works.
Constructors should create new objects. In your script, Person.new overrides everyone's name whenever you create a "new" Person. It should be implemented something like this:
function Person.new(name, age, eth)
local newPerson = {
Name = name,
Age = age,
Ethnicity = eth,
}
return setmetatable(newPerson, Person)
end
Constructors should not modify anything. They should just construct, that is, create.
When you're modeling things with objects, you can talk about a "has a" relationship.
Would say that a Person "has a" list of martial arts that they can use?
Then they need to be created with that field. Right now, they're not created with a set of martial arts:
function Person.new(name, age, eth)
local newPerson = {
Name = name,
Age = age,
Ethnicity = eth,
martialArts = {},
}
return setmetatable(newPerson, Person)
end
Methods should do something to a particular object. You want to have something like
function Person:LearnMartialArt(art)
table.insert(self.martialArts, art)
end
It may be appropriate for martial art objects (like art) to be its own class, or maybe just strings, or just tables.
However, that class is definitely unrelated to Person and should not be called Person.MartialArt, it should just be MartialArt.
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