Send for calling methods dynamically in Ruby - Step-by-Step Execution

Concept Flow - Send for calling methods dynamically

Start

↓

Have object

↓

Call send with method name as symbol/string

↓

send looks up method

↓

Method executed on object

↓

Return method result

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End

The send method takes a method name and calls that method on the object dynamically, returning the result.

Execution Sample

Ruby

class Greeter
  def hello
    "Hi!"
  end
end

obj = Greeter.new
puts obj.send(:hello)

This code calls the hello method dynamically on obj using send and prints the result.

Execution Table

Step	Action	Evaluation	Result
1	Create Greeter class with hello method	Defined class Greeter with method hello	Class ready
2	Create obj = Greeter.new	obj is new Greeter instance	obj created
3	Call obj.send(:hello)	send looks for method :hello on obj	Method found
4	Execute hello method	hello returns "Hi!"	"Hi!" returned
5	puts prints result	Output to console	Hi! printed

💡 send completed method call and returned result

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
obj	undefined	Greeter instance	Greeter instance	Greeter instance	Greeter instance
result	undefined	undefined	undefined	"Hi!"	"Hi!"

Key Moments - 3 Insights

Why do we use a symbol :hello instead of a string "hello" in send?

send accepts both symbols and strings, but symbols are preferred for method names because they are more efficient and commonly used in Ruby. See execution_table step 3 where :hello is passed.

What happens if the method name passed to send does not exist?

Ruby raises a NoMethodError because send tries to call a method that is not defined on the object. This is not shown here but would stop execution after step 3.

Can send call private methods?

Yes, send can call private and protected methods, bypassing normal access control. This is a powerful feature but should be used carefully.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of obj.send(:hello) at step 4?

A "Hi!"

B NoMethodError

C nil

D "hello"

💡 Hint

Check the 'Result' column at step 4 in execution_table

At which step does send look up the method on the object?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Action' and 'Evaluation' columns in execution_table for method lookup

If we change send(:hello) to send(:bye), what will happen?

A It will print nil

B It will print "Hi!" anyway

C It will raise NoMethodError

D It will call hello method

💡 Hint

Refer to key_moments about what happens if method does not exist

Concept Snapshot

Use send to call methods dynamically on an object.
Syntax: object.send(:method_name, args)
Method name can be symbol or string.
send bypasses access control (can call private methods).
Returns the method's result.
Raises error if method missing.

Full Transcript

This visual execution shows how Ruby's send method calls methods dynamically. First, a Greeter class with a hello method is defined. Then an object obj is created from Greeter. When obj.send(:hello) is called, send looks up the hello method on obj, executes it, and returns "Hi!". The puts prints this result. Variables obj and result change as the code runs. Beginners often wonder why symbols are used, what happens if the method is missing, and if send can call private methods. The quizzes check understanding of these steps and outcomes.