Introduction Flashcards
single line comment
comment
single line comment
comment
multi-line comment
=begin this is a multi line comment =end
Boolean
true or false
string
“just text”
prints a value in the console
puts
prints a value but adds a line break
methods
a “skill” or feature of an objec
.length
shows the length of characters in a string
.reverse
reverses a string
.upcase
capitalises an entire string
.downcase
converts a string to all lowercase
gets
retrieves user input
.chomp
removes a blank line
{variable}
retrieves variable data (user input) and inserts in a string
if
evaluates something to true or false
elsif
to insert another evaluations after an “if”
else
evaluates everything else if the first “if” or “elsif” are false
comparator
a sign that compares to values such as
== “is equal to”
< is less than
less than
>
greater than
<=
less than or equal to
> =
greater than or equal to
!=
not equal to
==
equal to
&&
and
||
or
!
not. reverses a true to false object to be the opposite
unless
an unless function, another version of “if”
runs a function unless the following is true
.gsub
substitutes a letter in a string ie
user_input.gsub (/s/, “th”)
the string “th” is what replaces every s
end
ends a if, else function
multi-line comment
=begin this is a multi line comment =end
Boolean
true or false
string
“just text”
prints a value in the console
puts
prints a value but adds a line break
methods
a “skill” or feature of an objec
.length
shows the length of characters in a string
.reverse
reverses a string
.upcase
capitalises an entire string
.downcase
converts a string to all lowercase
gets
retrieves user input
.chomp
removes a blank line
{variable}
String interpolation. retrieves variable data (user input) and inserts in a string
if
evaluates something to true or false
elsif
to insert another evaluations after an “if”
else
evaluates everything else if the first “if” or “elsif” are false
comparator
a sign that compares to values such as
== “is equal to”
< is less than
less than
>
greater than
<=
less than or equal to
> =
greater than or equal to
!=
not equal to
==
equal to
&&
and
||
or
!
not. reverses a true to false object to be the opposite
unless
an unless function. an action runs unless a condition is true
.gsub
substitutes a letter in a string ie
user_input.gsub (/s/, “th”)
the string “th” is what replaces every s
end
ends a if, else function
one-line If statement
an if statement can be written without and “end” if on one line
syntax
expression if boolean
ex.
puts “hello” if true
-> hello
one-line unless statment
no need for end
i.e.
puts “hello” unless 2*3 == 5
-> hello
ternary expression
a substitute for an if else statement. it takes three arguments: a boolean, an expression to evaluate if the boolean is true, and an expression to evaluate if the boolean is false.
syntax
boolean ? Do this if true: Do this if false
i.e.
puts 3 < 4 ? “3 is less than 4!” : “3 is not less than 4.”
| =
conditional assignment operator. assigns a real value to a variable only when its current value is false of nil. Otherwise ruby keeps its original value
i.e.
boyfriend = nil
boyfriend ||= “Jimmy Jr.”
boyfriend ||= “Josh”
puts boyfriend # => "Jimmy Jr."
short circuit evuation
for boolean operators && or ||, ruby will only evaluate to the point it is sure whether the statement is true or false.
.upto
iterates over values in a specific range upwards
i.e.
"B".upto("F") { |letter| print letter, " " }
# => B C D E F
.downto
iterates over values in a specific range downwards
i.e
5.downto(0) { |num| print num, “ “ }
# => 5 4 3 2 1 0
.respond_to?
takes a symbol representing a method name and returns true if that method can be called on the object and false otherwise.
puts "A".respond_to?(:push) # => false # Here, the following Ruby code will return false since .push can’t be called on a String object.
puts "A".respond_to?(:next) # => true # Here, however, the following Ruby code will return true since .next can be called on a String object. Calling .next on the letter “A” would return the letter “”.
<
concatenation operator. an alternative to push. can be used to add an element to the end of an array or a string
array = [1, 2, 3]
array «_space;4
print array
#Output => [1, 2, 3, 4]
puts "Hello," << " welcome to Codecademy." #Output => Hello, welcome to Codecademy.
