Implicit return (last expression) in Ruby - Step-by-Step Execution

Concept Flow - Implicit return (last expression)

Start method

↓

Evaluate expressions in method

↓

Last expression evaluated?

No→Continue evaluating

Yes↓

Return value of last expression

↓

End method

Ruby methods automatically return the value of the last expression evaluated without needing an explicit return statement.

Execution Sample

Ruby

def add(a, b)
  a + b
end

result = add(2, 3)
puts result

Defines a method that adds two numbers and returns the sum implicitly, then prints the result.

Execution Table

Step	Action	Expression Evaluated	Result	Return Value
1	Call add(2, 3)	Start method	N/A	N/A
2	Evaluate a + b	2 + 3	5	N/A
3	Last expression evaluated?	Yes	5	5
4	Method returns	Return value is 5	5	5
5	Assign to result	result = 5	5	5
6	Print result	puts 5	5	5

💡 Method ends after last expression; 5 is returned implicitly.

Variable Tracker

Variable	Start	After Step 2	After Step 5	Final
a	N/A	2	N/A	N/A
b	N/A	3	N/A	N/A
result	N/A	N/A	5	5

Key Moments - 2 Insights

Why does the method return 5 without an explicit return statement?

Ruby automatically returns the value of the last expression evaluated in the method, as shown in execution_table step 3 and 4.

What happens if there are multiple expressions in the method?

Only the last expression's value is returned implicitly; earlier expressions are evaluated but not returned, as seen in execution_table step 2.

Visual Quiz - 3 Questions

Look at the execution_table, what is the return value at step 4?

A 5

B 2

C 3

D N/A

💡 Hint

Check the 'Return Value' column at step 4 in the execution_table.

At which step is the expression 'a + b' evaluated?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Expression Evaluated' column in the execution_table.

If we add another expression after 'a + b', which expression's value will be returned?

A The sum of all expressions

B The first expression's value

C The last expression's value

D No value will be returned

💡 Hint

Refer to the concept_flow and key_moments about implicit return of the last expression.

Concept Snapshot

Ruby methods return the value of the last expression automatically.
No need to write 'return' explicitly.
All expressions before last are evaluated but not returned.
This makes code shorter and cleaner.
Example: def add(a,b); a + b; end returns a+b implicitly.

Full Transcript

In Ruby, when you define a method, you don't need to write 'return' to send back a value. The method automatically returns the value of the last expression it runs. For example, if you add two numbers inside a method, the sum is returned without writing 'return'. This is called implicit return. The execution table shows each step: starting the method, evaluating the sum, recognizing the last expression, returning its value, assigning it to a variable, and printing it. Variables 'a' and 'b' hold the input values, and 'result' holds the returned sum. Remember, only the last expression's value is returned, even if there are multiple expressions in the method.