Three things I learned from The Ruby Koans

Here are (at least) three things I learned from The Ruby Koans:

Blocks

I knew how to use blocks for methods that require them (like Array#each) but I didn’t have a grasp on how they worked outside of methods that I was familiar with.

Ruby blocks are little anonymous functions that can be passed into methods

Being told that Blocks are just as anonymous functions really helped it click— since I’m familiar with JS anonymous functions. I think the Block-syntax with pipes was just throwing me off 😅

Lambdas

Lamdas are a little weird because they’re basically just Blocks that have been defined and haven’t been run yet. You run them with .call.

say_something = -> { puts "This is a lambda" }
say_something.call

Procs

Procs are basically just lambdas. Lambdas are actually just a special kind of Proc.

proc = Proc.new { |arg| puts arg }

(meaning all three of these things are basically the same thing)

The differences are:

• procs don’t throw errors for missing arguments
• procs return from the current context

# Should work
my_lambda = -> { return 1 }
puts "Lambda result: #{my_lambda.call}"

# Should raise exception
my_proc = Proc.new { return 1 }
puts "Proc result: #{my_proc.call}"

If the proc was inside a method, then calling return would be equivalent to returning from that method. — RubyGuides