Exploring different ways to pass a function into a method in Ruby

Hello~ today I will to share a post about different ways of passing functions in Ruby.

There are many ways to pass code around in Ruby, so today I’m going to make a comparison between the 4 different ways. In this post, I will show the syntax of using each of them:

1. Block
2. Proc
3. Lambda
4. method(:func)

In the next post, I will compare the subtle differences they have.

A quick syntax comparison:

1. using a block

If we have a method call print_it which is expecting a method which takes an argument, like shown below:

method.rb
def print_it
  yield "hello world, block"
end

Let's try to pass in a method using a block with a do..end syntax:

passing_a_block.rb
print_it do |n|
  puts  "***" + n + "***"
end

result
*** hello world, block ***

2. using Proc.new

We'll explore how to use Proc. Let's say we have a method, that is expecting a Proc which takes an argument:

• note: while using a block, we call it using keyword yield, when using a proc, we use .call

method.rb
def print_it proc
  proc.call "hello world, proc"
end

passing_a_proc.rb
print_it(Proc.new do |n|
  puts "***" + n + "***"
end)

result
*** hello world, proc ***

One difference here is that a Proc can be stored in a variable:

store_proc_in_a_variable.rb
proc = Proc.new do |n|
  puts "***" + n + "***"
end

print_it(proc)

result
*** hello world, proc ***

3. using a Lambda

Now let's learn about how to use lambda, similarly, we begin by having a method like below: ghtly_smiling_face:

• note: using lambda is the same as proc, we need to use the keyword .call

lambda.rb
def print_it lambda
  lambda.call "hello world, lambda"
end

This is how we pass a lamda into the method:

passing_a_lambda.rb
print_it(lambda do |n|
  puts "***" + n + "***"
end)

result
*** hello world, lambda ***

4. using method(:some_method)

Again, we start with a method call

method.rb
def print_it code
  code.call "hello world, method"
end

passing_a_method.rb
def func n
  puts "***" + n "***"
end

print_it method(:func)

result
*** hello world, method ***

Summary

4 different ways are discussed in this post about how to pass a function call and how to execute it. In the next post the differences between these methods will be discussed .

Have a nice day~✿~❀ ~!