Ruby Method of the Day - String.<<

Posted by Kelly McCauley on Aug 31, 2007

Signature

string << other_string      #=> string
string.concat(other_string) #=> string
string << integer           #=> string  # integer must be between 0 and 255
string.concat(integer)      #=> string  # integer must be between 0 and 255

string.<< appends other_string or the ascii character equivalent of integer and returns itself.

Examples

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x = 'foo'
x << 'bar'            #=> "foobar"
y = 'fred'
y.concat('bob')       #=> "fredbob"

# Since x.<< returns itself, multiple calls to << will append to the first
# string object.
x << 'baz' << 'foz'   #=> "foobarbazfoz"
y.concat('bill').concat('alice')    #=> "fredbobbillalice"

z = 'a'
z << 98 << 99         #=> "abc"
z.concat(100)         #=> "abcd"

begin
  a = ''
  a << 1000
rescue Exception => e
  e.inspect           #=> #<TypeError: can't convert Fixnum into String>
end

Documentation Reference

www.ruby-doc.org : String.<<, String.concat

Ruby Method of the Day - String.+

Posted by Kelly McCauley on Aug 30, 2007

Signature

string + other_string   #=> new_string

string.+ returns a new string that is composed of string concatenated with other_string.

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"foo" + "bar"           #=> "foobar"
"foo".+("bar")          #=> "foobar"

x = 'foo'
y = 'bar'
z = 'baz'
x + ' ' + z + ' ' + y   #=> "foo baz bar"

Documentation Reference

www.ruby-doc.org : String.+

Ruby Method of the Day - String.*

Posted by Kelly McCauley on Aug 29, 2007

Signature

string * positive_integer   #=> new_string

string.* returns a new string that is composed of positive_integer copies of string.

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"x" * 5         #=> "xxxxx"
"x".*(5)        #=> "xxxxx"
"x" * 0         #=> ""

# * will not accept a negative integer
y = 'foo'
begin
  y * -2
rescue Exception => e
  e.inspect     #=> #<ArgumentError: negative argument>
end

Documentation Reference

www.ruby-doc.org : String.*