Little Things about Ruby Strings
Here are some things about Ruby Strings that may have escaped your attention - if you were introduced to Ruby via Rails
Efficiency
Since Ruby scans double-quoted strings for variables and escape sequences, it’s more efficient to use single-quotes for raw strings:
@sentence = 'Jackdaws love my big sphinx of quartz' redirect_to :index => 'action'
Pretty Please, with sugar on top …
Split your strings across multiple lines. No backslashes required (sorry, couldn’t resist that !).
sql_query = "SELECT [column]
FROM [table]
WHERE [condition]
-- sql comment goes here"or
# Q = double-quotes, embed variables # q = single-quotes sql_query = %Q{SELECT @columnname FROM @tablename WHERE @conditions} # You may use [ < or (as delimiters instead of {
ASCII code
To obtain the ASCII code for a character, prefix it with a question-mark:
puts ?B # => 66
Convert it back to a string with:
puts 66.chr # => "B"
Concatenation
Use the << operator to concatenate strings. Where += or + create a new copy, << appends to an existing string. Hence, it is more efficient:
existing << " end"Instead of:
existing += " end"(source)
Index a string with a regexp
You can test a string like this:
email = "spamandbakedbeans@skit.org" if email[/@/] puts "I found the first @" end
And this replaces the first match
string = "jackdaws love my big sphinx of quartz" string[/a/] = 'A' # => jAckdaws love my big sphinx of quartz
This replaces the second match
string = "jackdaws love my big sphinx of quartz" string[/(j).+(z)/, 2] = "Z" # => jackdaws love my big sphinx of quartZ
Remember, the regexp matches the entire string
Convert hex to integer (sort of)
Given a string representation of a hexadecimal, String.hex returns the corresponding integer:
puts "0x7b".hex # you can omit 0x if you wish # => 123
Multiply a string
puts "<br />" * 3 # => "<br /><br /><br />"
August 11th, 2007 at 2:08 pm
Hi,
well the efficiency gain between double and single quoted Strings - it’s hard to measure easily. Take for example this:
require ‘benchmark’
include Benchmark
LOOP_COUNT = 20000000
bm(12) do |test|
test.report(”Single quotes:”) do
LOOP_COUNT.times do |x|
str = ‘Jackdaws love my big sphinx of quartz’
str = ‘Yet another sentence, and what for? Benchmarking… Oh, dear.’
str = ”
end
end
test.report(”Double quotes:”) do
LOOP_COUNT.times do |x|
str = “Jackdaws love my big sphinx of quartz”
str = “Yet another sentence, and what for? Benchmarking… Oh, dear.”
str = “”
end
end
end
On my machine this yields the following result:
user system total real
Single quotes: 12.860000 0.040000 12.900000 ( 12.966023)
Double quotes: 12.810000 0.040000 12.850000 ( 12.896760)
And with the benchmarks swapped:
user system total real
Double quotes: 12.990000 0.040000 13.030000 ( 13.112319)
Single quotes: 12.950000 0.040000 12.990000 ( 13.025266)
Given the minor difference and the 60 Million there’s hardly any difference. That’s … not even a nano second per new String. So I wouldn’t think you should use single quoted Strings for performance.
Anyway I use both notations to indicate the real difference: If it’s single quoted it’s literally going to be taken ‘as is’ - with the exception of \\ \’ which are replaced in single quoted strings, too.
If a String is given with double quotes there will be some kind of variable interpolation or what ever else a single quoted String won’t process (e.g. a new line given as \n).
November 25th, 2007 at 2:42 pm
Hi ahsan,
Great job, with simple and objective samples.
May be you want to contribute with this:
http://en.wikibooks.org/wiki/Ruby_by_examples
Feel free to do that, with this and other subjects.