Ruby Cookbook, 2nd Edition

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Ruby Cookbook, 2nd EditionRecipes for Object-Oriented Scripting

Revised for Ruby 2.1, each recipe includes a discussion on why and how the solution works. You'll find recipes suitable for all skill levels, from Ruby newbies to experts who need an occasional reference. With Ruby Cookbook, you'll not only save time, but keep your brain percolating with new ideas as well.

Book Details

• Publisher:        O'Reilly Media
• By:        Lucas Carlson, Leonard Richardson
• ISBN:        978-1-44937-371-9
• Year:        2015
• Pages:        922
• Language:        English
• File size:        9.5  MB
• File format:        PDF
  

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关键词：Cookbook Edition editio dition Book reference includes solution experts recipes

1. 2.1 Building a String from Parts
   
2. Problem
   
3. You want to iterate over a data structure, and build a string from the data at the same time.
   
4. Solution
   
5. There are two efficient solutions. The simplest solution is to start with an empty string, and repeatedly append substrings onto it with the << operator:
   
6. hash = { key1: "val1", key2: "val2" }
   
7. string = ""
   
8. hash.each { |k,v| string << "#{k} is #{v}\n" }
   
9. puts string
   
10. # key1 is val1
    
11. # key2 is val2
    
12. This variant of the simple solution is slightly more efficient, but harder to read:
    
13. string = ""
    
14. hash.each { |k,v| string << k.to_s << " is " << v << "\n" }
    
15. If your data structure is an array, or easily transformed into an array, it’s usually more efficient to use Array#join:
    
16. puts hash.keys.join("\n") + "\n"
    
17. # key1
    
18. # key2

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1. 2.2 Substituting Variables into Strings
   
2. Problem
   
3. You want to create a string that contains a representation of a Ruby variable or expression.
   
4. Solution
   
5. Within the string, enclose the variable or expression in curly brackets and prefix it with a hash character:
   
6. number = 5
   
7. "The number is #{number}."                      # => "The number is 5."
   
8. "The number is #{5}."                           # => "The number is 5."
   
9. "The number after #{number} is #{number.next}."
   
10. # => "The number after 5 is 6."
    
11. "The number prior to #{number} is #{number-1}."
    
12. # => "The number prior to 5 is 4."
    
13. "We're ##{number}!"                             # => "We're #5!"

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1. 2.3 Substituting Variables into an Existing String
   
2. Problem
   
3. You want to create a string that contains Ruby expressions or variable substitutions, without actually performing the substitutions. You plan to substitute values into the string later, possibly multiple times with different values each time.
   
4. Solution
   
5. There are two good solutions: printf-style strings, and ERB (meaning “embedded Ruby”) templates.
   
6. Ruby supports a printf-style string format like C’s and Python’s. Put printf directives into a string and it becomes a template. You can interpolate values into it later using the modulus operator:
   
7. template = 'Oceania has always been at war with %s.'
   
8. template % 'Eurasia'  # => "Oceania has always been at war with Eurasia."
   
9. template % 'Eastasia' # => "Oceania has always been at war with Eastasia."
   
10. 
    
11. 'To 2 decimal places: %.2f' % Math::PI       # => "To 2 decimal places: 3.14"
    
12. 'Zero-padded: %.5d' % Math::PI               # => "Zero-padded: 00003"

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1. 2.4 Reversing a String by Words or Characters
   
2. Problem
   
3. The letters (or words) of your string are in the wrong order.
   
4. Solution
   
5. To create a new string that contains a reversed version of your original string, use the reverse method. To reverse a string in place, use the reverse! method:
   
6. s = ".sdrawkcab si gnirts sihT"
   
7. s.reverse                            # => "This string is backwards."
   
8. s                                    # => ".sdrawkcab si gnirts sihT"
   
9. 
   
10. s.reverse!                           # => "This string is backwards."
    
11. s                                    # => "This string is backwards."
    
12. To the order of the words in a string, split the string into a list of whitespaceseparated words, then join the list back into a string:
    
13. s = "order. wrong the in are words These"
    
14. s.split(/(\s+)/).reverse!.join('')   # => "These words are in the wrong order."
    
15. s.split(/\b/).reverse!.join('')      # => "These words are in the wrong. order"

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1. 2.5 Representing Unprintable Characters
   
2. Problem
   
3. You need to make reference to a control character, a strange UTF-8 character, or some other character that’s not on your keyboard.
   
4. Solution
   
5. Ruby gives you a number of escaping mechanisms to refer to unprintable characters. By using one of these mechanisms within a double-quoted string, you can put any binary character into the string.
   
6. You can reference any binary character by encoding its octal representation into the format "\000", or its hexadecimal representation into the format "\x00":
   
7. octal = "\000\001\010\020"
   
8. octal.each_byte { |x| puts x }
   
9. # 0
   
10. # 1
    
11. # 8
    
12. # 16
    
13. 
    
14. hexadecimal = "\x00\x01\x10\x20"
    
15. hexadecimal.each_byte { |x| puts x }
    
16. # 0
    
17. # 1
    
18. # 16
    
19. # 32
    
20. This makes it possible to represent UTF-8 characters even when you can’t type them or display them in your terminal. Try running this program, and then opening the generated file smiley.html in your web browser:
    
21. open('smiley.html', 'wb') do |f|
    
22.   f << '<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">'
    
23.   f << "\xe2\x98\xBA"
    
24. end

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1. 2.6 Converting Between Characters and Values
   
2. Problem
   
3. You want to see the ASCII code for a character, or transform an ASCII code into a string.
   
4. Solution
   
5. To see the ASCII code for a specific character as an integer, use the String#ord method:
   
6. "a".ord                 # => 97
   
7. "!".ord                 # => 33
   
8. "\n".ord                # => 10
   
9. To see an individual character of a particular string, access it as though it were an element of an array:
   
10. 'a'[0]                  # => "a"
    
11. 'bad sound'[1]          # => "a"
    
12. 
    
13. 'a'[0].ord              # => 97
    
14. 'bad sound'[1].ord      # => 97
    
15. To see the ASCII character corresponding to a given number, call its #chr method. This returns a string containing only one character:
    
16. 97.chr              # => "a"
    
17. 33.chr              # => "!"
    
18. 10.chr              # => "\n"
    
19. 0.chr               # => "\x00"
    
20. 256.chr             # RangeError: 256 out of char range

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1. 2.7 Converting Between Strings and Symbols
   
2. Problem
   
3. You want to get a string containing the label of a Ruby symbol, or get the Ruby symbol that corresponds to a given string.
   
4. Solution
   
5. To turn a symbol into a string, use Symbol#to_s, or Symbol#id2name, for which to_s is an alias:
   
6. :a_symbol.to_s                        # => "a_symbol"
   
7. :AnotherSymbol.id2name                # => "AnotherSymbol"
   
8. :"Yet another symbol!".to_s           # => "Yet another symbol!"
   
9. You usually reference a symbol by just typing its name. If you’re given a string in code and need to get the corresponding symbol, you can use String.intern:
   
10. :dodecahedron.object_id               # => 516488
    
11. symbol_name = "dodecahedron"
    
12. symbol_name.intern                    # => :dodecahedron
    
13. symbol_name.intern.object_id          # => 516488

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