Crystal Programming Language Cheatsheet

Crystal is a statically-typed, compiled programming language with a syntax that resembles Ruby. It is designed to be efficient, expressive, and statically checked, making it an excellent choice for developers who appreciate the benefits of both static typing and a clean, concise syntax. Whether you’re a beginner getting started with Crystal or an experienced developer looking for a quick reference guide, this cheatsheet is here to help you navigate the essentials of the Crystal programming language.

Hello World

   puts "Hello, World!"

Variables and Constants

   # Variables
   name = "Crystal"
   age = 5

   # Constants
   VERSION = "1.0.0"

Data Types

   # Basic types
   number = 42
   float_number = 3.14
   is_true = true
   text = "Crystal is awesome!"

   # Arrays and Hashes
   numbers = [1, 2, 3, 4]
   person = {"name" => "Alice", "age" => 30}

Control Flow

   # If statement
   if condition
     # code to execute when condition is true
   else
     # code to execute when condition is false
   end

   # Case statement
   case variable
   when value1
     # code to execute when variable equals value1
   when value2
     # code to execute when variable equals value2
   else
     # code to execute when none of the values match
   end

Loops

   # While loop
   while condition
     # code to execute while condition is true
   end

   # For loop
   for item in collection
     # code to execute for each item in the collection
   end

Functions

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

   # Calling a function
   message = greet("Bob")

Classes and Objects

   # Defining a class
   class Person
     property name : String
     property age : Int32

     def initialize(@name : String, @age : Int32)
     end

     def greet
       "Hello, #{@name}!"
     end
   end

   # Creating an object
   person = Person.new("Alice", 30)
   puts person.greet

Exception Handling

   begin
     # code that might raise an exception
   rescue ex : SomeException
     # handle the exception of type SomeException
   else
     # code to execute if no exception is raised
   ensure
     # code that always executes, whether an exception is raised or not
   end

Modules and Includes

   # Defining a module
   module MyModule
     def my_method
       "This is a method from MyModule"
     end
   end

   # Including a module in a class
   class MyClass
     include MyModule
   end

   obj = MyClass.new
   puts obj.my_method

Concurrency

Crystal provides built-in support for lightweight concurrency with fibers. However, a detailed discussion of concurrency in Crystal is beyond the scope of this cheatsheet.

Conclusion

This cheatsheet covers the fundamental aspects of Crystal programming, providing a quick reference for common syntax and constructs. For more in-depth information, refer to the official Crystal documentation at https://crystal-lang.org/docs/.

Crystal’s combination of speed, readability, and expressiveness makes it a compelling language for a wide range of applications. Whether you’re building web applications, scripting, or tackling system-level programming, Crystal offers a powerful and enjoyable development experience. Use this cheatsheet as a starting point to accelerate your Crystal programming journey!

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