17-structs.md

Structs

Rugo structs provide lightweight object-oriented programming using hashes with dot access. They work naturally with the require namespace system — a struct file acts as a "class."

Defining a Struct

struct Dog
  name
  breed
end

This creates a constructor function Dog(name, breed) that returns a hash with those fields, plus a new() alias for use with namespaces.

Dot Access on Hashes

Any hash supports dot notation for field access:

person = {"name" => "Alice", "age" => 30}
puts person.name          # Alice
person.name = "Bob"       # write access
puts person.name          # Bob

Nested dot access works too:

data = {"user" => {"name" => "Alice"}}
puts data.user.name       # Alice

Methods

Define methods on a struct type with def Type.method(). The first parameter self is added automatically:

# dog.rugo
struct Dog
  name
  breed
end

def Dog.bark()
  return self.name + " says woof!"
end

def Dog.rename(new_name)
  self.name = new_name
end

Methods are called through the namespace after requiring the struct file:

require "dog"

rex = dog.new("Rex", "Labrador")
puts dog.bark(rex)            # Rex says woof!
dog.rename(rex, "Rexy")
puts dog.bark(rex)            # Rexy says woof!

Structs with Namespaces

The namespace acts as the "class" — dog.new() creates instances, dog.bark(rex) calls methods.

Type Introspection

Use type_of() to get the type name of any value. For structs, it returns the struct name:

rex = Dog("Rex", "Lab")
puts type_of(rex)            # Dog
puts type_of("hello")        # String
puts type_of(42)             # Integer

See Also

• examples/structs/ for a full working example
• docs/modules.md for the require/namespace system