Crystal Methods — Def, Return Types, Named Arguments and Blocks

DodaTech Updated 2026-06-29 1 min read

In this tutorial, you will learn about Crystal Methods. We cover key concepts, practical examples, and best practices to help you master this topic.

Crystal methods combine Ruby's flexible syntax with static Type Checking. Every method has a known return type, inferred or declared.

Basic Methods

def greet(name : String) : String
  "Hello, #{name}!"
end

puts greet("Alice")  # => Hello, Alice!

# Without return type (inferred)
def add(a, b)
  a + b
end

# Default arguments
def create_url(host, port = 443, path = "/")
  "https://#{host}:#{port}#{path}"
end

Blocks and Yield

def twice
  yield
  yield
end

twice { puts "Hello" }
# Output: Hello (twice)

# With arguments
def each_item(items)
  items.each { |item| yield item }
end

each_item([1, 2, 3]) { |x| puts x * 10 }

← Previous Crystal Control Flow — if, unless, case, while, and until Next → Crystal Classes — Inheritance, Abstract Classes, and Method Overrides

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