Using Ruby’s gsub with a hash
Hacker. Emacs fanatic. Lover of parentheses. Firebrand. Just another programmer with too many opinions. I’m not the best, but I’m pretty good. Recently we discussed how you can use String#gsub with a block. Today we’ll examine another somewhat unknown feature of the gsub method - the ability to supply a replacement hash as the second argument (which is normally a string). If the replacement argume
Ruby’s magic underscore
I discovered today that Ruby treats underscores a little bit differently when it comes to variable names. Suppose, for the sake of argument, that we have a set of data that looks like this: people = { "Alice" => ["green", "[email protected]"], "Bob" => ["brown", "[email protected]"] } and we want to ignore eye colour and age and convert each element to a simple array containing name and email addr
Delegate: Make your object speak on behalf of another object
Random Ruby and Rails tips. This blog is dedicated to deliver short, interesting and practical tidbits of the Ruby language and Ruby on Rails framework. Read more... Your submissions are more than welcome! Delegate: Make your object speak on behalf of another object Say you have a one-to-many relationship between two models and you need to use this relationship to do some calculations. For example
StackOverflow cool Ruby questions 4 - Khaled alHabache’s official blog
Welcome to the fourth post of this series. Just before proceeding to the questions, I would like to mention the great Metaprogramming Ruby: Program Like the Ruby Pros book by Paolo Perrotta, a very good book that explains the metaprogramming aspects of the Ruby language. Now let’s get going! Scope gates Taken from the above mentioned book: There are exactly three places where a program leaves the
Route 477 - Ruby 1.9.2のリリースプランが発表 (7月末リリース予定)
■ [ruby] Hashのデフォルト値にHashを設定しようとしてはまった話 h = {} ary.each do |x, y, z| h[x] ||= {} h[x][y] = z end をもっと短くしようとして、 h = Hash.new{ {} } ary.each do |x, y, z| h[x][y] = z end としたら上手く動かない。あれっ？ デフォルト値が{}じゃなくて数値の場合、例えば h = Hash.new{ 0 } ary.each do |x| h[x] += 1 end みたいのはちゃんと動くわけです。上のとどう違う？ h[x][y] = z はどういう動作になるか考えてみよう。 hにxというキーがある場合： h[x]というハッシュに、(y, z)のペアを保存。 hにxというキーがない場合： ブロックが呼ばれて、その値が返る。返り値であるハッシュに、(
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After writing my last post on Rails plugin idioms, I realized that Ruby metaprogramming, at its core, is actually quite simple. It comes down to the fact that all Ruby code is executed code--there is no separate compile or runtime phase. In Ruby, every line of code is executed against a particular self. Consider the following five snippets: class Person def self.species "Homo Sapien" end end class
"Newbie" Feedback
I recently had the privilege to supply the challenge for the second ever Ruby Programming Challenge For Newbies. I thought it pretty cool that the challenge provoked 40+ "newbies" to submit responses. As one might expect, there was some rough Ruby, but very few butcherings of the language. In the spirit of the code review, I tried to provide constructive feedback to all participants. Following is
Route 477(2009-09-28)
■ [ruby] Structを使って簡単にクラスを定義するtips Structを使うと、いちいちattr_readerとか書かなくていいのが楽だし、オープンクラス使えばメソッド追加だってできる。 Identifier = Struct.new(:tag, :attributes) class Identifier attr_accessor :text def initialize(t, a={}) super(t, a) end end …という話は知ってる人が多いと思うけど、同じことをこう書いてる例を見つけて驚いた。 celerity / lib / celerity / identifier.rb Identifier = Struct.new(:tag, :attributes) do attr_accessor :text def initialize(t, a={}) su
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True, False And Nil Objects In Ruby
Every expression and every object in Ruby has a boolean value, which means that every object and every expression must either evaluate to true or to false. This makes true and false rather special values. But, they are not just empty value or simple keywords, just like with everything else, both true and false are Ruby objects. The True And False Objects You’re probably aware that true and false a
Ruby On Rails ピチカート街道 - ひらがなの「あ」と表示する6つの方法 -
ひらがな１文字って言ったってバイトに分解してみれば、そりゃあいろいろ取り出せまっせ。 ひらがなの「あ」をバイト列を使って表示する方法が色々あるので、載せておきます。 # 以下の例は UTF-8 です # その壱：ノーマル puts "あ" # その弐：符号あり10進数 puts [-29, -127, -126].pack("c*") # その参：符号なし10進数 puts [227, 129, 130].pack("C*") # その四：8進数 puts "\343\201\202" # その伍,その六：16進数 puts ["e38182"].pack("H*") puts "\xe3\x81\x82" # ちなみにEUC-JP puts "\xa4\xa2" # ちなみにShift_JIS puts "\x82\xa0"
module って super できたんだ - まめめも
module D def foo p :D end end module C def foo p :C super end include D end module B def foo p :B super end include D end class A def foo p :A super end include C include B end A.new.foo #=> :A, :B, :C, :D :A, :B, :D, :C, :D かなとも思ったけど違った。これって多重継承と何か違うんかな。そもそも菱形継承問題の何が問題なのかわかってない。
Ruby On Rails ピチカート街道 - rubyでハッシュのハッシュのハッシュとかを簡単に作る方法 -
Perlだと、特に宣言なしに、 $a{'size'}{'upperbody'}{'chest'} = 100; とか出来るのに Ruby だといちいち Hash.new() など宣言しなくてはならず不便です！ しかし以下のおまじないを唱えると、ハッシュのハッシュのハッシュとかを一気に宣言できちゃって便利ったらありゃしません。 my_hash = Hash.new{|h,k| h[k]=Hash.new(&h.default_proc)} my_hash[:size][:upperbody][:chest] = 100 my_hash[:size][:egg] = 'XL' my_hash => {:size=>{:upperbody=>{:chest=>100}, :egg=>"XL"}} というのが使い方で、とっても便利ですね、いろんな場面で使えそうです！ 以下は、なんでーそうなるの？と
Method Arguments In Ruby
Method arguments in Ruby are interesting because of the great flexibility in how you’re allowed to supply them to methods. Ruby method arguments can loosely be broken up into two categories, required arguments and optional arguments. However, I like to break them up into three categories (I hope it will become clear by the end of this post why I do so): required arguments arguments with default va
has_many :bugs, :through => :rails: Ruby I don't like #2 - catch(:wtf) { throw :wtf }
The 1960s and 1970s saw computer scientists move away from GOTO statements in favor of the structured programming programming paradigm. Some programming style coding standards prohibit use of GOTO statements. – Wikipedia Ruby takes the whole GOTO nonsense to an entirely new heights. Ruby’s version of GOTO/LABEL is called throw/catch. The lunacy goes further as Ruby’s throw is equivalent to GOTO wi
has_many :bugs, :through => :rails: Ruby I don't like #1 - Explicit 'return'
In Ruby, you don’t have to specify an explicit return value from a method. A Ruby will just return the last evaluated statement. Similarly, if an explicit return statement will make itself the last evaluated statement – i.e return control to the caller with the specified return value. However, I’m not a big fan of explicit return statements. In my experience, the only place where they make sense i
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has_many :bugs, :through => :rails: Ruby I don't like #3 - Object#freeze