Separate number by commas, format phone

Separate number by comma with using `gsub`:

def separate_by_comma(number)
  number.to_s.reverse.gsub(/(\d{3})/, '\1,').reverse
end

without:

def spearate_by_comma(number)
  number.to_s.chars.reverse.each_slice(3).map(&:join).join(",").reverse
end

Rails: STI (Single Table Inheritance)

	class User < ActiveRecord::Base
	has_many :animals
	has_many :dogs
	has_many :cats
	end
	class Zoo < ActiveRecord::Base
	has_many :animals
	has_many :elephants
	end
	class Animal < ActiveRecord::Base
	# for STI should have additional field `type`
	scope :domestic, -> { where("user_id IS NOT NULL").includes(:user) }
	end
	class Elephant < Animal
	belongs_to :zoo
	end
	class Dog < Animal
	belongs_to :user
	end
	class Cat < Animal
	belongs_to :user
	end
	user = User.first
	user.animals # -> [<Dog:...>, <Cat:...> ..]
	user.dogs # -> [<Dog:...>, ..]
	user.cats # -> [<Cat:...>, ..]
	zoo = Zoo.first
	zoo.animals # -> [<Elphant:...>, ..]
	zoo.elephants # -> [<Elphant:...>, ..]
	Animals.all # -> [<Dog:...>, <Cat:...>, <Elephants:..>, ..]
	Dogs.all # -> [<Dog:...>, ..]
	Cats.all # -> [<Cat:...>, ..]
	Elephant.all # -> [<Elephants:...>, ..]
	Animals.domestic # -> [<Dog:...>, <Cat:...> ..]

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Rust: macros notation

	//
	// #[item_attribute] - attribute for module or file
	//
	// #![crate_attribute] - attribute for crate
	//
	// - #[attribute = "value"]
	// - #[attribute(key = "value")]
	// - #[attribute(value)]
	//
	// #![crate_type = "lib"] - crate as library (instead `--crate-type` compile param)
	// #![crate_name = "something"] - library is named "something"
	//
	#[cfg(target_os = "linux")]
	fn are_you_on_linux() {
	println!("you are running linux!")
	}
	#[cfg(not(target_os = "linux"))]
	fn are_you_on_linux() {
	println!("you are *not* running linux!")
	}
	#[cfg(not(some_key))]
	fn conditional_function() {
	println!("you don't pass `--cfg some_key`!")
	}
	#[cfg(some_key)]
	fn conditional_function() {
	println!("you just pass `--cfg some_key`!")
	}
	// allow unused code
	#[allow(dead_code)]
	// allow camel case type names
	#[allow(non_camel_case_types)]
	// add default Show trait implementation to struct
	#[deriving(Show)]
	struct SomeStructure (int, int);
	fn main() {
	are_you_on_linux();
	conditional_function();
	println!("test deriving Show - {}", SomeStructure(1,2));
	}

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Rust: some notation about Trait methods

	// file_1.rs
	//
	// implement class method and instance method with the same name
	//
	struct Car {
	stamp: &'static str
	}
	impl Car {
	fn print() {
	println!("It is Car class method!")
	}
	}
	trait Print {
	fn print(&self) -> ();
	}
	impl Print for Car {
	fn print(&self) {
	println!("It is Car instance method")
	}
	}
	fn main() {
	let car = Car { stamp: "BMW" };
	Car::print();
	car.print();
	}
	// file_2.rs
	//
	// traits couldn't implement class methods
	// but could implement class methods which return Self (because with
	// type it knows what implementation should use)
	//
	struct Car {
	stamp: &'static str
	}
	impl Car {
	fn print(&self) {
	println!("It is Car instance with stamp: {}", self.stamp)
	}
	}
	trait Face {
	fn print() -> ();
	fn new(var: &'static str) -> Self;
	}
	impl Face for Car {
	fn print() {
	println!("It is Car class method!")
	}
	fn new(var: &'static str) -> Car {
	Car { stamp: var }
	}
	}
	fn main() {
	// Car::print(); // first-class methods are not supported
	// Face::print(); // cannot determine a type for this bounded type parameter: unconstrained type
	// let car = Face::new("BMV"); // cannot determine a type for this bounded type parameter: unconstrained type
	let car: Car = Face::new("BMV");
	car.print();
	}

view raw rust-class-method-and-trait.rs hosted with ❤ by GitHub