Ruby Tricks

1. Object#tap

If you have a method which updates one key in hash, you need to add return that hash in the

end of method.

	def update_params(params)
	params[:foo] = 'bar'
	params
	end

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But you can use Object#tap !

	def update_params(params)
	params.tap { |p| p[:foo] = 'bar' }
	end

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The result will be equal

2. bsearch

If you need to use "find" in a big sorted Array, change method to bsearch

	require 'benchmark'
	data = (0..50_000_000)
	Benchmark.bm do |x|
	x.report(:find) { data.find {|number| number > 40_000_000 } }
	x.report(:bsearch) { data.bsearch {|number| number > 40_000_000 } }
	end

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        user        system      total        real
find      3.020000   0.010000   3.030000   (3.028417)
bsearch  0.000000   0.000000  0.000000   (0.000006)

3. Flat_map

If you have two or more "map" methods, and as a result you get multidimensional array like [[1,2], [[3],4]]].

	module CommentFinder
	def self.find_for_users(user_ids)
	users = User.where(id: user_ids)
	users.map do |user|
	user.posts.map do |post|
	post.comments.map |comment|
	comment.author.username
	end
	end
	end
	end
	end

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[[['Ben', 'Sam', 'David'], ['Keith']], [[], [nil]], [['Chris'], []]]

What can you do? You can use method flatten after each "map"

	module CommentFinder
	def self.find_for_users(user_ids)
	users = User.where(id: user_ids)
	users.map { |user|
	user.posts.map { |post|
	post.comments.map { |comment|
	comment.author.username
	}.flatten
	}.flatten
	}.flatten
	end
	end

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But it will be shorter to use "flat_map" instead of "map"

	module CommentFinder
	def self.find_for_users(user_ids)
	users = User.where(id: user_ids)
	users.flat_map { |user|
	user.posts.flat_map { |post|
	post.comments.flat_map { |comment|
	comment.author.username
	}
	}
	}
	end
	end

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http://apidock.com/ruby/Enumerable/flat_map

4. new Array

Quickly create two-dimensional array with zeros

	Array.new(8)
	{ Array.new(8) { ‘0’ } }

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5.  Comparison

You can use comparison "<=>" for time issue. If you pass time in minutes and return hours.

	def fix_minutes
	until (0...60).member? minutes
	@hours -= 60 <=> minutes
	@minutes += 60 * (60 <=> minutes)
	end
	@hours %= 24
	self
	end

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6. Deep copy

object.clone - give you the same object, scilicet reference

Marshal.dump(obj) - give you a new object (new object_id)

7. Rub Ruby

How to run code in terminal without creating ruby file?

ruby -e "code_here"

8. Quick bool

Concert any value to the Boolean

!!(1)   # true
!!(nil) # false

9. What is "and"

Code

code: d = 1 and e = 2 and false and f = 3

result d = 1 e = 2 f = nil

Info from
blog.engineyard.com

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