Introduction to Ruby Page 4/5

IV. Embed strings
One of the functions I like very much in Ruby is to embed strings. The so-called embed refers to the form of writing variables directly into quotes. The advantage of this is that it is intuitive and saves the frequency of hyphens. For example, in C# we can write the following code.


string val = "value";
 string printVal = "value: " + val;
 // or
 string printVal = ("value: {0}", val);

But in Ruby, you can use the form of embedded strings to save some code (I think the elegance of Ruby is reflected here).


 val = "Value"
printVal = "value: #{val}"

Embedding strings is very simple, just put the variable name in the braces after the # character. For class variables, member variables and global variables, even curly brackets can be omitted (braces cannot be omitted for pseudo-variables).


1module Company
 2 class Employee
 3 # Class variables
 4 @@companyName = ".org"
 5 # Member variables
 6 @empId
 7
 8 def setEmpId(val)
 9 @empId = val
 10 end
 11
 12 def display()
 13 # Braces omitted
 14 print "Company: #@companyName\n"
 15 print "Employee ID: #@empId\n"
 16 # Braces cannot be omitted for pseudo-variables
 17 print "lines: #{__LINE__}\n"
 18 end
 19 end
 20end
 twenty one
 22emp = Company::
 ("001")

Ruby's embedded strings can only be used in double quotes, because the interpreter will output the contents in single quotes as is. Ruby's single quotes feel like @"" in C#.


# Output as is
 # Company: #@@companyName
 print 'Company: #@companyName'
 # output as-is (including spaces and line breaks)
 print '
 Company: .org
 Employee Id: unknown

% rendered

Another cool feature of Ruby is the % rendering method, which is an alternative to quotes or other delimited characters. It is wrong to directly insert double quotes into double quotes in the first sentence below, but after rendering with % you can directly insert double quotes into the string.


# mistake
 print "Ruby"% presentation method""
 # Apply % rendering method
 print %Q#Ruby "% rendering"#

In % rendering, Q is the rendering identifier and ! is the rendering separator. The rendering identifier declares which delimiter character to replace, ! is a custom delimiter. The rendering delimiter is as long as the front and back are consistent, but the letters and < characters cannot be selected as the rendering delimiter. If you want to insert rendering characters in the rendering method, you must use the \ character.


# correct
 print %Q~Ruby "% rendering"~
 print % "% rendering".
 print %Q*Ruby "% rendering"*
 # Insert rendering delimiter in % rendering
 print %Q*\* Ruby "% rendering"*
 # mistake
 print %Q** Ruby "% rendering"*
 print %QbRuby "% rendering"b
 print %Q<Ruby "% render"<

% render list
%Q substitute for double quotes => %Q#Ruby "% rendering"# is equivalent to "Ruby \"% rendering\""
%q replaces single quotes
%r replaces regular expression => %r#([\d\w/])*# is equivalent to /([\d\w\/)*/
%s invalidates embedded strings and symbols => print %s@#{__LINE__}@ output as is
%w Alternative string array

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