Strings

Ref. WGR Chapter 8, Section 8.1, Working with strings

String literals

• double-quotes "foo"
  • allow interpolation, e.g. "Welcome, #{name}"
• single-quotes 'foo'
  • no interpolation
• %Q -- %Q{don't worry, "man"}
  • just like double-quote only you don't need a backslash for "
• %q -- %q{don't #{interpolate}, "man"}
  • just like single-quote only you don't need a backslash for '
• %Q, %q -- any delimiter will do
  • %Q|...|, %Q{...}, %Q(...), etc.

Multiline strings

• newlines do not end a string

    "Now is the winter of our discontent
    made glorious summer by this son of York."
  

=>

    "now is the winter of our discontent\nmade glorious summer by this son of York."

Here Docs

first_quatrain = <<END
My mistress' eyes are nothing like the sun;
Coral is far more red than her lips' red;
If snow be white, why then her breasts are dun;
If hairs be wires, black wires grow on her head.
END

Here docs with indentation

def second_quatrain
  x = <<-HTML
    <blockquote>
      I have seen roses damask'd, red and white,
      But no such roses see I in her cheeks; 
      And in some perfumes is there more delight
      Than in the breath that from my mistress reeks.
    </blockquote>
  HTML
  x
end

Here docs don't have to end the expression

@@@ruby
x = <<-NUM.to_i * 10
5
NUM
x  # => 50

Weird, huh?

substrings

@@@ruby
s = "Ruby rocks"
s[5]    #=> "r"
s[5,3]  #=> "roc"
s[5,100]  #=> "rocks"
s[-3]   #=> "c"
s[2..6] #=> "by ro"

substring matching

@@@ruby
s = "Ruby rocks"
s[/r../] #=> "roc"
s[/r../i] #=> "Rub"

substring setting

@@@ruby
s = "Ruby rocks"
s["rock"] = "rule"
s #=> "Ruby rules"

adding strings

s = "xyz" 
s + "pdq"  #=> "xyzpdq"
s          #=> "xyz"

s = "xyz"
s << "pdq" #=> "xyzpdq"
s          #=> "xyzpdq"

string interpolation

Takes any ruby expression, calls to_s on it, and smooshes it inside a string

"nothing compares #{1+1} u" #=> "nothing compares 2 u"

string interpolation - advanced

anything can go in there, including operators and quotes

"i love #{girlfriend or "nobody"}"

nil.to_s is the empty string, which can be convenient

"i love #{girlfriend.name if girlfriend}"

string comparison

"a" < "b"    #=> true
"a" < "A"    #=> false
"a" <=> "b"  #=> -1

• Array#sort uses <=>
  • the "flying saucer" operator
• String#== compares the characters in each string

gsub

s.gsub(/xyz/, "pdq")

• performs a regular expression search-and-replace on the string
• gsub! modifies the string in place

split

"apple banana cherry".split
=> ["apple", "banana", "cherry"]

• turns a string into an array
• splits on whitespace by default
  • or you can pass in a delimiter
• join turns an array into a string

Digression: A Ruby Idiom

@@@ ruby
title.split.map{|s|s.capitalize}.join(' ')

• this technique is called method chaining
• each operation changes the result of the previous operation
• in this case, it
  • splits a title into words
  • capitalizes each word
  • joins the words back together

more string methods

• s.upcase
• s.downcase
• s.capitalize
• s.strip
  • removes whitespace, not clothes, from the ends of the string
• s.chomp
  • removes the final character, but only if it's a "\n"
• s.center(width)
• s.delete(substr)

some of these have ! versions which modify the string in place