MCQs on Object-Oriented Programming in Lua | Lua

Master Object-Oriented Programming (OOP) in Lua to build efficient, reusable code. Explore simulating classes with tables, utilizing metatables, implementing inheritance, polymorphism, objects, and methods effectively in Lua scripts.

MCQs: Object-Oriented Programming in Lua

Simulating Classes with Tables and Metatables

1. How are classes commonly simulated in Lua?
   • a) Using functions
   • b) Using tables
   • c) Using metatables
   • d) Using global variables
2. What role do metatables play in simulating OOP in Lua?
   • a) They define the behavior of tables.
   • b) They create global variables.
   • c) They execute conditional logic.
   • d) They manage memory allocation.
3. Which function is used to assign a metatable to a table?
   • a) setmetatable(table, metatable)
   • b) assign_metatable(table, metatable)
   • c) usemetatable(table, metatable)
   • d) apply_metatable(table, metatable)
4. What is the __index metamethod used for in Lua?
   • a) To handle errors in table indexing
   • b) To define default behavior for missing keys
   • c) To initialize variables
   • d) To lock the table structure
5. How do you create a constructor in a Lua class simulation?
   • a) Define a function that returns a table
   • b) Define a global variable
   • c) Use new() function directly
   • d) Call init() function automatically
6. What happens when the __call metamethod is defined in a metatable?
   • a) The table can be called like a function.
   • b) The table is made immutable.
   • c) The table becomes read-only.
   • d) The table can no longer use metamethods.
7. In Lua, which operator uses the __index metamethod to access a key in a table?
   • a) +
   • b) -
   • c) . (dot operator)
   • d) : (colon operator)
8. Which metamethod is used to customize equality checks for Lua objects?
   • a) __eq
   • b) __add
   • c) __concat
   • d) __call
9. What is the result of setting a metatable’s __index to the table itself?
   • a) Infinite recursion
   • b) A cyclic reference error
   • c) A valid table lookup with fallback
   • d) No effect
10. How can you define a method in a table to simulate an object’s behavior?
    • a) Use the : operator
    • b) Use the . operator
    • c) Use the [] operator
    • d) Use the => operator

Inheritance and Polymorphism

11. How is inheritance typically achieved in Lua?
    • a) By copying methods from one table to another
    • b) By assigning __index in the child table to the parent table
    • c) By calling inherit() function
    • d) By using global variables
12. What is polymorphism in the context of Lua programming?
    • a) The ability to reuse the same function names in different contexts
    • b) The process of defining global variables
    • c) The concept of memory allocation
    • d) The behavior of tables without metatables
13. How do you override a parent method in Lua inheritance?
    • a) Define a method with the same name in the child table
    • b) Modify the parent table directly
    • c) Use super.method_name()
    • d) Use the __call metamethod
14. What happens if a method is not found in the child table during inheritance?
    • a) Lua throws an error.
    • b) The method is searched in the parent table.
    • c) The method is ignored.
    • d) Lua exits the program.
15. Which metamethod allows you to customize how Lua performs addition for an object?
    • a) __add
    • b) __index
    • c) __eq
    • d) __call
16. How do you call a parent method explicitly in Lua inheritance?
    • a) Use ParentTable.method(self, args)
    • b) Use self:method(args)
    • c) Use ParentTable::method(self, args)
    • d) Use method(self, args)
17. Which keyword is typically used for polymorphism in Lua?
    • a) local
    • b) self
    • c) super
    • d) Lua does not have a specific keyword for polymorphism.
18. What does the :new() method typically do in Lua OOP?
    • a) Creates a new object instance
    • b) Deletes a table
    • c) Resets the state of a table
    • d) Sets the __index metamethod
19. What is the result of using multiple inheritance in Lua?
    • a) Undefined behavior without explicit handling
    • b) Automatic conflict resolution
    • c) Error during execution
    • d) Multiple methods being overridden
20. How do you ensure shared behavior among multiple Lua objects?
    • a) Use shared metatables
    • b) Copy methods manually
    • c) Avoid using metatables
    • d) Use global variables

Implementing Objects and Methods

21. How do you define a method for an object in Lua?
    • a) Use the : syntax when defining the function
    • b) Use the . syntax when defining the function
    • c) Use the [] syntax when defining the function
    • d) Use the => syntax when defining the function
22. What is the significance of the self parameter in Lua methods?
    • a) It refers to the current object instance.
    • b) It refers to the parent table.
    • c) It refers to the global table.
    • d) It refers to a new table.
23. What is the difference between . and : in Lua?
    • a) : implicitly passes self to the function, whereas . does not.
    • b) : is for inheritance, and . is for polymorphism.
    • c) : works with metatables only, and . works with global tables.
    • d) There is no difference.
24. What happens if you forget to include self in a method definition?
    • a) The method will not have access to the object instance.
    • b) Lua will throw an error.
    • c) The method will call the parent method.
    • d) Lua will implicitly include self.
25. Which method is typically used to initialize object properties in Lua?
    • a) new()
    • b) init()
    • c) __init()
    • d) setup()
26. How do you add a new method to an existing Lua object?
    • a) Assign the function directly to the object.
    • b) Use add_method() function.
    • c) Call append_method() on the object.
    • d) Create a new metatable.
27. How can you prevent direct modification of an object’s properties in Lua?
    • a) Use the __newindex metamethod.
    • b) Use the __call metamethod.
    • c) Use the __index metamethod.
    • d) Set the table as immutable.
28. What is the benefit of using metatables in Lua for object implementation?
    • a) They enable custom behavior and method delegation.
    • b) They increase execution speed.
    • c) They simplify syntax.
    • d) They ensure global access.
29. How do you associate an object with a class in Lua?
    • a) Use setmetatable() with the class’s metatable.
    • b) Use attach() function.
    • c) Use link() function.
    • d) Use set() function.
30. What is the output of calling an object method using the : operator?
    • a) The method is called with the object instance as the first argument.
    • b) The method is called without arguments.
    • c) The method is called with the parent table.
    • d) The method cannot be called with the : operator.

Answer Table