Method declaration with def in Ruby - Step-by-Step Execution

Concept Flow - Method declaration with def

Start

↓

Write def method_name

↓

Add method body

↓

End with 'end'

↓

Method ready to call

↓

Call method to run code

↓

Execute method body

↓

Return result or nil

↓

End

This flow shows how to declare a method using def, write its body, end it, and then call it to run the code inside.

Execution Sample

Ruby

def greet
  puts "Hello!"
end

greet

This code declares a method greet that prints Hello! and then calls it.

Execution Table

Step	Action	Evaluation	Output
1	Define method greet	Method greet created
2	Call greet	Method greet starts
3	Execute puts "Hello!"	Prints Hello!	Hello!
4	Method greet ends	Returns nil
5	Program ends	No more code

💡 Method greet finished execution and program ends

Variable Tracker

Variable	Start	After 1	After 2	Final
Method greet	undefined	defined	called	defined

Key Moments - 2 Insights

Why do we need the 'end' keyword after the method body?

The 'end' keyword tells Ruby where the method finishes. Without it, Ruby doesn't know where the method stops, causing errors. See execution_table step 4 where method ends.

What happens if we call the method before defining it?

Ruby will give an error because the method doesn't exist yet. The method must be defined first as shown in execution_table step 1 before calling it in step 2.

Visual Quiz - 3 Questions

Look at the execution table, what is printed when the method greet is called?

A "greet"

B "Hello!"

C Nothing

D An error message

💡 Hint

Check execution_table row 3 where puts "Hello!" outputs Hello!

At which step does the method greet finish execution?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at execution_table row 4 where method greet ends and returns nil

If we remove the 'end' keyword, what will happen?

A The method will run normally

B The method will return nil automatically

C Ruby will raise a syntax error

D The method will print "end"

💡 Hint

Refer to key_moments about the importance of 'end' keyword and execution_table step 4

Concept Snapshot

def method_name
  # method body
end

- Use def to start method declaration
- Write code inside method body
- Close with end keyword
- Call method by its name to run
- Methods return last evaluated value or nil

Full Transcript

This visual trace shows how to declare a method in Ruby using def. First, we write def followed by the method name. Then we add the code inside the method body. We finish the method with the end keyword. After defining, we call the method by its name to run the code inside. The example method greet prints Hello! when called. The execution table shows each step: defining the method, calling it, printing output, and ending the method. Variables track the method state from undefined to defined and called. Key moments explain why the end keyword is needed and why methods must be defined before calling. The quiz tests understanding of output, method end step, and syntax errors without end.