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Enumable#grep

レシーバと引数が===と一致するかどうかで絞り込む
# ===で一致するか、ということは==の条件に「範囲ないか」「インスタンス、クラスに属するか」「正規表現に一致するか」は加わったもの

(1..10).grep(2..3)               #=> [2, 3]
%w|a 1 * @|.grep(/[1-9]/)        #=> ["1"]
["a", 1, "&", "@"].grep(Integer) #=> [1]

grepの良い所は条件でしぼりこんだあとにブロックを渡して更に処理ができる

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Hash#find_all
Hash#select

h = {a: 1, b: 2, c: 3}
h.find_all { |key, value| value.odd? } #=> [[:a, 1], [:c, 3]]
h.select   { |key, value| value.odd? } #=> {:a=>1, :c=>3}

Array#select
Array#select

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# map(collect)

### 特徴
レシーバの配列の要素、１つずつに対して処理を行う  
一つずつというのが重要で、処理前と処理後の配列のsizeは結局同じ  

### 使い所
配列→配列の場合に使う  
配列内容の要素すべてを１つずつ同様の処理を行うのに便利  
例えば  

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# []があるから範囲指定の文字列抽出用途では価値ない
"2012-08-01".slice(0..2)
"2012-08-01"[0..2]

# 正規表現で抽出文字列を絞り込めるはおおきな利点
"2012-08-01".slice(/-(.+)-/) # => "-08-"
# ちなみにdeleteは削除後の文字列を返却するのが違い
"2012-08-01".delete(/-(.+)-/) # => "201201"

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# 02
message = "hello"
if message.length > 1
 alert message

# 03
s = "hello 
safdaf
asdf
asfdfda"

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numbers = [1, 2, 3, 4, 5, 6]

result1 = []
numbers.each do |num|
  result1 << num * 2 if num % 2 == 0
end

p result1  # => [4, 8, 12]

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# A sample Guardfile
# More info at https://github.com/guard/guard#readme

guard 'livereload' do
  watch(%r{app/views/.+\.(erb|haml|slim)$})
  watch(%r{app/helpers/.+\.rb})
  watch(%r{public/.+\.(css|js|html)})
  watch(%r{config/locales/.+\.yml})
  # Rails Assets Pipeline
  watch(%r{(app|vendor)(/assets/\w+/(.+\.(css|js|html|png|jpg))).*}) { |m| "/assets/#{m[3]}" }

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bundle exec guard
01:12:33 - INFO - Guard is using TerminalTitle to send notifications.
01:12:33 - INFO - Guard::RSpec is running
01:12:33 - INFO - Guard is now watching at '/Users/kyuden/Test'
[1] guard(main)> 
01:12:34 - INFO - Run all
01:12:34 - INFO - Running all specs
WARN: Unresolved specs during Gem::Specification.reset:
      rspec-expectations (~> 2.14.0)
      rspec-mocks (~> 2.14.0)

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describe vs. context in rspec
http://lmws.net/describe-vs-context-in-rspec

In Rspec world, you often see people using both “describe” blocks and “context” blocks together, like this

describe "launch the rocket" do
  context "all ready" do
  end
 
  context "not ready" do

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# display remote_branch
gir branch -r

# clone remote_branch on local
git checkout 'branch_name' origin/'branch_name'