Ruby Default Arguments

Default arguments in Ruby allow developers to specify fallback values for method parameters. This feature enhances code flexibility and reduces the need for multiple method definitions.

Syntax and Usage

To define a method with default arguments, assign a value to the parameter in the method definition:

def greet(name = "World")
  puts "Hello, #{name}!"
end

greet        # Output: Hello, World!
greet("Ruby") # Output: Hello, Ruby!

In this example, "World" is the default value for the name parameter. If no argument is provided when calling the method, it uses the default value.

Multiple Default Arguments

Ruby methods can have multiple default arguments:

def create_user(name, age = 30, role = "Member")
  puts "Created user: #{name}, Age: #{age}, Role: #{role}"
end

create_user("Alice")                # Output: Created user: Alice, Age: 30, Role: Member
create_user("Bob", 25)              # Output: Created user: Bob, Age: 25, Role: Member
create_user("Charlie", 35, "Admin") # Output: Created user: Charlie, Age: 35, Role: Admin

Best Practices

• Place parameters with default values at the end of the parameter list.
• Use default arguments to make methods more flexible and reduce the number of method overloads.
• Choose meaningful default values that make sense in the context of your application.
• Be cautious when using mutable objects as default values, as they persist between method calls.

Default Arguments and Ruby Keyword Arguments

Default arguments can be combined with keyword arguments for even more flexibility:

def configure(host: "localhost", port: 8080, ssl: false)
  puts "Configuring: Host: #{host}, Port: #{port}, SSL: #{ssl}"
end

configure                     # Uses all defaults
configure(port: 3000)         # Overrides only the port
configure(ssl: true, host: "example.com") # Overrides host and ssl

This approach allows callers to specify only the arguments they want to override, making the method highly customizable.

Considerations

When working with default arguments, keep these points in mind:

• Default values are evaluated at method invocation time, not definition time.
• You can use Ruby variables or expressions as default values.
• Default arguments work well with Ruby method overriding in inheritance scenarios.

By mastering default arguments, you can write more concise and flexible Ruby code, reducing duplication and improving maintainability.