How do you substring a string in Ruby?
There is no substring method in Ruby. Instead we rely upon ranges and expressions. Substring ranges. With a range, we use periods in between 2 numbers—the first and last index of the substring.
How do you check if a string contains a letter in Ruby?
Use the  Syntax to Check Whether a String Contains a Substring in Ruby. For accessing a character in a string at a specific index, we could use the  syntax. The interesting thing about this syntax is that if we pass in a string, it will return a new string that is matched; otherwise, it will return nil .
What is $1 in Ruby?
In short, $1, $2, $… are the global-variables used by some of the ruby library functions specially concerning REGEX to let programmers use the findings in later codes.
What is =~ in Ruby?
=~ is Ruby’s basic pattern-matching operator. When one operand is a regular expression and the other is a string then the regular expression is used as a pattern to match against the string. (This operator is equivalently defined by Regexp and String so the order of String and Regexp do not matter.
What does each_char do in Ruby?
The each_char in Ruby is used to pass each character that makes a string to a block in Ruby. The block of each_char takes a single parameter which represents characters in a string.
What is the difference between GSUB and sub?
Sub versus gsub. The sub() method replaces just the first instance of a string with another. Gsub meanwhile replaces all instances. Thus:Gsub is closest to a “replace string” method. Sub() is conceptually a “replace first string” method.
The question mark gives the regex engine two choices: try to match the part the question mark applies to, or do not try to match it. The engine always tries to match that part. Only if this causes the entire regular expression to fail, will the engine try ignoring the part the question mark applies to.
What is the difference between string interpolation and concatenation?
Concatenation allows you to combine to strings together and it only works on two strings. Swift uses string interpolation to include the name of a constant or variable as a placeholder in a longer string, and to prompt Swift to replace it with the current value of that constant or variable.