Ruby-CheatSheet.md

Ruby Methods

String Methods

A new string is returned, unless a bang (!) is added after the method (for example, .split!) which mutates the original string.

METHOD	FUNCTION
.strip	removes the leading and trailing whitespace on strings
.chomp	removes the last character in a string, only if it's a carriage return or new line
.upcase	makes all characters in a string UPCASE
.downcase	makes all characters in a string DOWNCASE
.class	describes the class of an object
.object_id	returns the integar identifier for an object
.length	returns the number of characters in a string (incl. whitespace)
.count	counts how many time a specific character is found in string - for example, "HELLO".count('L')
.insert	inserts a string into another string before a given index - for example, "Hello".insert(3, "hi5") -> Helhi5lo
.capitalise	makes the first letter in a string uppercase and the rest downcase
.reverse	reverses the order of characters in a string - for example, "Hello World!".reverse -> "!dlroW olleH"
.split	takes string and splits it into an array, then returns the array default method splits based on whitespace, unless different separator provided ("" to split by character; " " to split by word)
.chop	removes the last character of the string - for example, "Batman".chop -> "Batma"
.pop	removes the last letter in a string and returns it - for example, "Linda".pop would return "a"
.include?("STRING")	to test if a string is included in another
.index("STRING")	looks for partial words, returns index where the start of this string is found
to_s	converts data type to string
to_i	convert data type to integar
to_f	convert data type to float
to_sym	convert data type to symbol
<<	string concatenation
.each_char	returns an array of characters in a string
.gsub	to replace text in a string: for example, for string = "We have many dogs", method would be string.gsub("dogs", "cats")

Sub-String Methods

METHOD	FUNCTION
string = "abc123"	Below examples use this string
string[x,y]	x = starting index, y = number of characters you want - for example string[3,3] -> 123
string[0..-2]	get characters within a range - first index is starting, second is ending index (inclusive)
(1..10).to_a	[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
('A'..'Z').to_a	creates an array of alphabetical letters - for example ["A", "B", "C", "D", "E", "F"]

Number Methods

METHOD	FUNCTION
.abs	returns the absolute (positive) version of an integar/float
.round	rounds float to a given precisio in decimal digits, default is 0 - for example, .round(2) -> two decimal places

Array Methods

METHOD	FUNCTION
.join	takes an array of strings and joins them into a single string, can pass a character separator as an argument
.length	tallies the number of elements inside an array
.first	accesses the first element of the array
.last	accesses the last element of the array
.take	returns the first 'n' elements of the array - for example, arr = [0, 1, 2, 3, 4], the function and result would be arr.take(3) -> [0, 1, 2]
.drop	returns the elements after 'n' elements of an array
.pop	permanently remove the last element of an array
.shift	permanently remove the first element of an array, returns element
.push	to add an element to the end of an array - for example, arr.push(99) -> [0, 1, 2, 3, 4, 99]
.unshift	add an element to the beginning of an array arr.unshift(1) -> [1, 2, 3]
.delete	removes a specified element from an array permanently
.delete_at	permanently remove an element of an array from a specified index
.reverse	reverses the array but does not mutate it
.select	iterates over an array and returns a new array that includes values that return true
.is_a? Integar	iterates through an array to check Class type.

Conversion Functions

METHOD	FUNCTION
.to_i	convert to integer
.to_f	convert to float
.to_s	convert to string
.to_sym	convert to symbol
.to_a	convert to array