Strings and Symbols

1. STRINGS AND SYMBOLS
Sarah Allen

2. STRINGS
• “I am a string!”

3. QUOTING STRINGS
• Double quotes interpolate
>> me = "double quotes are awesome”
>> "I am a string withsdouble quotes.n #{me}"
=> "I am a string with double quotes.n double quotes are
awesome"
• Single quotes don’t interpolate
>> 'I am a string withssingle quotes.n #{me}'
=> "I am a string withssingle quotes.n #{me}"

4. CONCATENATING STRINGS
first_name = "Yukihiro”
last_name = "Matsumoto”
full_name = first_name + " " + last_name
=> "Yukihiro Matsumoto"

5. STRING INTERPOLATION
birthday = “January 5th”
“My birthday is #{birthday}”

6. STRING FORMATTING:
UPCASE
>> full_name.upcase >> full_name.upcase!
=> "YUKIHIRO MATSUMOTO” => "YUKIHIRO MATSUMOTO"
>> full_name >> full_name
=> "Yukihiro Matsumoto" => "YUKIHIRO MATSUMOTO"

7. MORE STRING
FORMATTING
>> full_name.downcase!
=> "yukihiro matsumoto"
>> full_name.capitalize
=> "Yukihiro matsumoto"
• Making our own title case method:
>> full_name.split.map {|w| w.capitalize}.join(" ")
=> "Yukihiro Matsumoto"
• We can also get title case using regex

8. ACCESS A STRING’S
CHARACTERS
>> full_name[2,4]
=> "kihi"
>> full_name[4..6]
=> "hir"

9. RUBY 1.8
>> name = "Yukihiro”
=> "Yukihiro”
>> name[4]
=> 104
>> name[4].chr
=> "h"
>> name = " ”
=>"343201223343202223343201204343201241343
20221”
>> name[2]
=> 147

10. RUBY 1.9
>> name = "yukihiro”
=> "yukihiro”
>> name[4]
=> "h”
>> name = " ”
=> " ”
>> name[2]
=> " ”
>> name[0]
=> " "

11. MODIFYING A STRING
>> full_name.slice!("hi")
=> "hi"
>> full_name
=> "yukiro matsumoto"
>> full_name["hi"] = "bye"
=> "bye"
>> full_name
=> "Yukibyero Matsumoto"
>> full_name[4,2] = "bye"
=> "bye"
>> full_name
=> "Yukibyero Matsumoto"

12. QUERY A STRING
>> full_name.include?("hi")
=> true
>> full_name.empty?
=> false
>> full_name.size
=> 18
>> full_name.count("o")
=> 3

13. ITERATE OVER A STRING
• each_line: process each line in a string
haiku = "5n7n5n”
haiku.each_line{|line| puts line}
5
7
5
 each_char: process character
 each_byte: process each byte careful of 1.8.x and 1.9 differences
>> word = " " >> word = " "
=> " " => " "
>> word.each_char do |s| puts
>> word.each_byte do | s
end
s|
puts s
end
227
129

14. ITERATE USING SPLIT
• returns an array of partial strings exploded at a separator
secret_code = "the black dove flies at night”
secret_code.split(" ").each do |s|
puts s.reverse
end
eht
kcalb
evod
seilf
ta
thgin

15. MORE STRING OPERATIONS
full_name = ""
=> ""
full_name << first_name
=> "Yukihiro"
full_name << " "
=> "Yukihiro "
full_name << last_name
=> "Yukihiro Matsumoto"

16. MORE STRING OPERATIONS
"foo " * 3
=> "foo foo foo "

17. SYMBOLS
• :i_am_a_symbol

18. WHAT IS A SYMBOL?
• A symbol represents a name.
• Instances of the built-in class Symbol.
• They efficiently describe names while saving the space
one would use to generate a string for each naming
instance.

19. A SYMBOL IS NOT A
STRING
:thing != “thing”
• However a symbol can be create from a string:
“thing”.to_sym
• And a string can be created from a symbol
:thing.to_s

20. SYMBOLS ARE IMMUTABLE
• You can’t change a symbol
• For example, you can’t append characters to a symbol...once a symbol exists,
that’s it!
>> :name + :me
NoMethodError: undefined method `+' for :name:Symbol
from (irb):182
from :0
>> :name << :me
NoMethodError: undefined method `<<' for :name:Symbol
from (irb):183
from :0

21. SYMBOLS ARE UNIQUE
• :name is the only symbol object called :name
>> :name.object_id
=> 68828
>> :name.object_id
=> 68828
• “name” is a new String object each time it is instantiated
>> "name".object_id
=> 2157595700
>> "name".object_id
=> 2157591380