A.4 String

A.4.1 .concat (.+)

String#concat(Integer) ⇒ String

String#concat(String) ⇒ String

Appends the given arguments to a string. when given an integer as an argument, it converts the integer into ASCII code.

"hi".concat(33) # => "hi!"

"Rub".concat(121)  # => "Ruby"

When given a string literal as an argument, it adds that string to the original string. .+ or + is similar to the .concat method. + will return a new combined String instead of modifying the original String. Each line of code below will give the same output.

"hi".concat(" there")
"hi".+(" there")
"hi" +(" there")
"hi" + " there"

This method returns a new String

Full explanation

A.4.2 * method

Multiplies the original string by the given integer and returns the new modified String.

"Ya" * 5

Returns "YaYaYaYaYa"

"Ya" * 0

Returns ""

Full explanation

A.4.3 .upcase

String#upcase ⇒ String

Converts all lowercase letters to their uppercase counterparts in the given string and returns the new modified String.

"hello".upcase`

Returns

"HELLO"

Full explanation

A.4.4 .downcase

String#downcase ⇒ String

Converts all the uppercase letters to their lowercase counterparts from the given String. Returns the new modified String.

"HI".downcase`

Returns

"hi"

Full explanation

A.4.5 .swapcase

String#swapcase ⇒ String

Converts all the uppercase letters to their lowercase counterparts and lowercase letters to their uppercase counterparts from the given string. Returns the new modified String.

"Hi There".swapcase

Returns

"hI tHERE"

"hI tHERE".swapcase

Returns

"Hi There"

Full explanation

A.4.6 .reverse (String)

String#reverse ⇒ String

Returns a new String with the characters from the original String in reverse order.

"stressed".reverse

Returns

"desserts"

Full explanation

A.4.7 .length

String#length ⇒ Integer

Returns the Integer number of charactersin the String.

"hippopotamus".length

Returns

12

Full explanation

A.4.8 .chomp

String#chomp ⇒ String

String#chomp(String) ⇒ String

When not given any argument, removes the "\n" (newline) character from the end of the string. When given an argument of a charcter or a string, it remove that argument from the end of the orginal string.

Returns a new String with the character removed.

"Hey!\n".chomp  
"Hey!".chomp("!")  
"Hey There".chomp("There")  
"Hey!".chomp("y")

"Hey!"  
"Hey"  
"Hey "  
"Hey!"

p "What is your name?"
name = gets # supposes the user inputs "Clark" and then hits return
p "Hi" + name

Prints

"Hi Clark\n"

p "What is your name?"
name = gets # supposes the user inputs "Clark" and then hits return
p "Hi" + name.chomp

Prints

"Hi Clark"

p "What is your name?"
name = gets.chomp # supposes the user inputs "Clark" and then hits return
p "Hi" + name

"Hi Clark"

Full explanation

A.4.9 .gsub

String#gsub(String, String) ⇒ String

Substitutes the all occurances of the first argument with the second argument in original string and returns a new String with the substitutes made.

"Hello".gsub("ello", "i")

Returns

"Hi"

"Hi.there".gsub(".", " ")

Returns

"Hi there"

Giving an empty string as the second arugment deletes any occurences of the first arugument in the string.

"example @ ruby.com".gsub(" ", "")

Returns

"example@ruby.com"

Full explanation

A.4.10 .to_i (String)

String#to_i ⇒ Integer

Converts a string literal that contains a number to an integer. The Integer is returned.

"8".to_i

Returns

8

p "What is your lucky number?"
lucky_number = gets.chomp # Suppose the user types is "7" and then hits return
square = lucky_number ** 2 # This will throw an error.

Returns

NoMethodError (undefined method '**' for "7":String)

This is where the .to_s method comes handy.

p "What is your lucky number?"
lucky_number = gets.chomp # Suppose the user types is "7" and then hits return
square = lucky_numbe.to_i ** 2 # This will throw an error.
p square

Returns

"49"

Full explanation

A.4.11 .strip

String#strip ⇒ String

Removes all leading and trailing whitespace in the string.

Returns a new String that has been modified from the original.

"   hi there ".strip

Returns

"hi there"

Full explanation

A.4.12 .capitalize

String#capitalize ⇒ String

Capitalizes the first character of a string.

Returns a new String that has been modified from the original.

"capitalize".capitalize

Returns

"Capitalize"

Full explanation

A.4.13 .split

String#split ⇒ Array

String#split(String) ⇒ Array

Splits a string into an substrings and creates an Array of these substrings. when not given argument, .split uses whitespace to divide the string. when given an argument, .split divides the string on that argument.

Returns an Array of the divided String.

"Hello hi byebye".split

Returns

["Hello", "hi", "byebye"]

"one!two!three!".split("!")

Returns

["one", "two", "three"]

Full explanation

A.4.14 .include?

String#include?(String) ⇒ Boolean

Returns a boolean(true or false) based on whether the string argument is inside the string the method is being called on.

"Happy".include?("H")

Returns

true

"Happy".include?("Z")

Returns

false

Full explanation