Parameters with default values in Ruby - Step-by-Step Execution

Concept Flow - Parameters with default values

Define method with default parameters

↓

Call method with arguments?

No→Use default values

Yes↓

Assign passed arguments to parameters

↓

Execute method body

↓

Return result

↓

End

The method is defined with default values for parameters. When called, if arguments are missing, defaults are used; otherwise, passed values are used.

Execution Sample

Ruby

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

puts greet("Alice")
puts greet

Defines a method with a default parameter and calls it with and without an argument.

Execution Table

Step	Method Call	Parameter 'name'	Action	Output
1	greet("Alice")	"Alice"	Use passed argument	"Hello, Alice!"
2	puts output	-	Print output	Hello, Alice!
3	greet	"Friend"	Use default value	"Hello, Friend!"
4	puts output	-	Print output	Hello, Friend!
5	-	-	End of calls	-

💡 No more method calls; execution ends.

Variable Tracker

Variable	Start	After Call 1	After Call 2	Final
name	-	"Alice"	"Friend"	-
output	-	"Hello, Alice!"	"Hello, Friend!"	-

Key Moments - 2 Insights

Why does the method use "Friend" when no argument is given?

Because the parameter 'name' has a default value "Friend" defined, so when no argument is passed (see execution_table row 3), it uses that default.

What happens if we pass an argument to the method?

The passed argument overrides the default value (see execution_table row 1), so 'name' becomes the passed value.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'name' during the second method call?

A nil

B "Alice"

C "Friend"

D "Hello"

💡 Hint

Check execution_table row 3 where the method is called without arguments.

At which step is the output "Hello, Alice!" printed?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at execution_table row 2 where puts prints the output.

If we change the default value to "Guest", what will be printed at step 4?

A "Hello, Guest!"

B "Hello, Friend!"

C "Hello, nil!"

D "Hello, Alice!"

💡 Hint

Refer to variable_tracker for default value changes affecting output.

Concept Snapshot

def method_name(param = default)
  # method body
end

- If argument is passed, param = argument
- If no argument, param = default
- Allows flexible calls with optional arguments

Full Transcript

This example shows how Ruby methods can have parameters with default values. When the method greet is called with an argument like "Alice", it uses that value. When called without an argument, it uses the default "Friend". The execution table traces each call and output. The variable tracker shows how 'name' changes. This helps beginners understand how default parameters work in Ruby methods.