Section 1
Preview this deck
What does the .split method do?
Front
| 5 | 0 | ||
| 4 | 0 | ||
| 3 | 0 | ||
| 2 | 0 | ||
| 1 | 0 |
Active users
0
All-time users
0
Favorites
0
Last updated
6 years ago
Date created
Mar 1, 2020
Cards (150)
Section 1
(50 cards)
What does the .split method do?
Ruby has a built-in method for this called .split; it takes in a string and returns an array. If we pass it a bit of text in parentheses, .split will divide the string wherever it sees that bit of text, called a delimiter. For example, text.split(",") tells Ruby to split up the string text whenever it sees a comma. www.codecademy.com
How can you create a hash, other way than? hash = {}
hash = Hash.new www.codecademy.com
What does the next do in this loop? i = 20 loop do i -= 1 next if i % 2 == 0 print "#{i}" break if i <= 0 end
i = 20 loop do i -= 1 next if i % 2 == 0 print "#{i}" break if i <= 0 end Modulo www.codecademy.com
What do the two methods "gets" and ".chomp" do in the example below? variable_name = gets.chomp
gets is the Ruby method that gets input from the user. When getting input, Ruby automatically adds a blank line (or newline) after each bit of input; chomp removes that extra line. (Your program will work fine without chomp, but you'll get extra blank lines everywhere.) www.codecademy.com
What does the interpreter do?
The interpreter is the program that takes the code you write and runs it. www.codecademy.com
true or false true || true # => true || false # => false || true # => false || false # =>
true || true # => true true || false # => true false || true # => true false || false # => false www.codecademy.com
Why are exclamation marks used in ruby methods?
In general, methods that end in ! indicate that the method will modify the object it's called on. Ruby calls these "dangerous methods" because they change state that someone else might have a reference to.
Create hash using literal notation hash = { key1 => value1, key2 => value2, }
hash = { "foo" => "bar", "greet" => "hey" } www.codecademy.com
How can you write "Foo" with all letter uppercase and lowercase?
"foo".upcase "foo".downcase www.codecademy.com
How do you create an array in Ruby with values "foo" and "bar"?
my_array = ["foo", "bar"] www.codecademy.com
Add a pet called named Stevie, which is a cat to the pets = {}
pets = {} pets["Stevie"] = "cat" www.codecademy.com
What is the difference between output from print and puts?
The print command just takes whatever you give it and prints it to the screen. puts (for "put string") is slightly different: it adds a new (blank) line after the thing you want it to print. www.codecademy.com
Is access by index the same thing as index by offset?
yes it is www.codecademy.com
What is going on here? What would be output? array = [1,2,3,4,5] array.each do |x| x += 10 print "#{x}" end
10 is being added to each array item output would be 1112131415 www.codecademy.com
How would extract the key value pairs from the following hash? family = { "Homer" => "dad", "Marge" => "mom", "Lisa" => "sister", "Maggie" => "sister", "Abe" => "grandpa", "Santa's Little Helper" => "dog" }
family.each { |x, y| puts "#{x}: #{y}" } or family.each do |x, y| puts "#{x}: #{y}" end www.codecademy.com
How can you retrieve what kind of animal is Bowser from the hash? pets = { "Stevie" => "cat", "Bowser" => "hamster", "Kevin Sorbo" => "fish" }
pets["Bowser"] www.codecademy.com
What does "puts" stand for?
print string www.codecademy.com
Is possible to combine boolean into expressions?
yes, it is! Combinations like (x && (y || w)) && z are not only legal expressions, but are extremely useful tools for your programs. Expressions in parentheses are always evaluated before anything outside parentheses. www.codecademy.com
How would you acces "swiss" in the sandwiches array? sandwiches = [["ham", "swiss"], ["turkey", "cheddar"], ["roast beef", "gruyere"]]
sandwiches[0][1] www.codecademy.com
What does a until loop do?
It's sort of like a backwards while: It will execute its code while the condition it checks is false. As soon as that condition becomes true, the loop will end. www.codecademy.com
What will be the output of this declaration? "anton".capitalize
"Anton" www.codecademy.com
How is this operation called and what does it do? 25 % 7 = ?
Modulo Modulo returns the remainder of division. For example, 25 % 7 would be 4, since 7 goes into 25 3 times with 4 left over. www.codecademy.com
When would you use a for loop?
Sometimes you do know how many times you'll be looping, however, and when that's the case, you'll want to use a for loop. for num in 1...10 puts num end www.codecademy.com
What does the method below do? if string_to_check.include? "substring"
It check if the string contains a substring "substring". If it does found one, it will evaluate to true, otherwise it will evaluate to false. www.codecademy.com
When we loop over an array or a hash, we say that we ... over it.
iterate www.codecademy.com
How can you write "foo" backward using a certain method?
"foo".reverse www.codecademy.com
true or false !true # => !false # =>
!true # => false !false # => true www.codecademy.com
In Ruby, curly braces ({}) are generally interchangeable with the keywords ... (to open the block) and ... (to close it).
In Ruby, curly braces ({}) are generally interchangeable with the keywords do (to open the block) and end (to close it). www.codecademy.com
How would you find a square root of 9?
Math.sqrt(9) https://www.ruby-lang.org/en/documentation/quickstart/ www.codecademy.com
How can you check what methods exist for the Greeter objects? How can you exclude ancestors from the list? class Greeter ... end
Greeter.instance_methods In order to exclude ancestors, you may use: Greeter.instance_methods(false) https://www.ruby-lang.org/en/documentation/quickstart/3/
To what does the counter equal to using the following operators. counter = 100 counter += 100 # => counter -= 100 # => counter *= 100 # => counter /= 100 # =>
counter = 100 counter += 100 # => 200 counter -= 100 # => 0 counter *= 100 # => 10000 counter /= 100 # => 1 www.codecademy.com
When will program output "I'm writing Ruby programs!" unless hungry puts "I'm writing Ruby programs!" else puts "Time to eat!" end
When variable hungry would equal to false. www.codecademy.com
Perform a puts using the .times operator to output "foo" 10 times
10.times { puts "foo"} or 10.times do puts "foo" end www.codecademy.com
What kind of an array is this? multi_d_array = [[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0]]
multidimensional www.codecademy.com
How can you get out of this loop? i = 20 loop do i -= 1 print "#{i}" ... if i <= 0 end
i = 20 loop do i -= 1 print "#{i}" break if i <= 0 end www.codecademy.com
How can you check the length of the sting "I love ruby"?
"I love ruby".length www.codecademy.com
To what do method evaluate in Ruby, which end with "?"?
It evaluates to a boolean value, true or false. www.codecademy.com
What does "anton".capitalize! mean?
fix this card ASAP www.codecademy.com
How is this operation called and what does it do? 2**3 = ?
Exponentiation Exponentiation raises one number (the base) to the power of the other (the exponent). 2**3 = ? 222 = 8 www.codecademy.com
What is the difference between: for num in 1...15 puts num end for num in 1..15 puts num end
for num in 1...15 puts num end Will not output 15 for num in 1..15 puts num end Will output 15 www.codecademy.com
What does ".gsub!" method stand for? And what does it do?
global substitution It substitutes a substring, with another one. string_to_change.gsub!(/s/, "th") www.codecademy.com
What are good naming conventions for Ruby variables?
Variables should start with a lowercase letter and words should be separated by underscores, like counter and masterful_method. Ruby won't stop you from starting your local variables with other symbols, such as capital letters, $s, or @s, but by convention these mean different things, so it's best to avoid confusion by doing what the Ruby community does. www.codecademy.com
What does the respond_to? do?
Returns true if obj responds to the given method. Private and protected methods are included in the search only if the optional second parameter evaluates to true. http://ruby-doc.org/core-2.2.2/Object.html#method-i-respond_to-3F
true or false? true && true # => true && false # => false && true # => false && false # =>
true && true # => true true && false # => false false && true # => false false && false # => false www.codecademy.com
Write a while loop, which has a variable counter, which = to 1 and add 1 each iteration until variable counter will equal to 11.
counter = 1 while counter < 11 puts counter counter += 1 end www.codecademy.com
How can you output a variable with in a string (using string interpolation). first_name = "Kevin" Output should be this: Your name is Kevin
first_name = "Kevin" puts "Your name is #{first_name}" www.codecademy.com
What does the "++" and the "--" operator do in Ruby?
Nothing, these operators do not exist in ruby. Use += or -= instead. www.codecademy.com
What is a hash in Ruby?
A hash is a collection of key-value pairs. Hash syntax looks like this: hash = { key1 => value1, key2 => value2, key3 => value3 } Values are assigned to keys using =>. You can use any Ruby object for a key or value. www.codecademy.com
How do you write a multi-line comment in ruby?
=begin Hello, there! I am a very nice comment. =end www.codecademy.com
How would you quit irb shell (shortcut)?
ctrl + d
Section 2
(50 cards)
Create a hash called my_hash and give it any default value other than nil.
no_nil_hash = Hash.new("Horse power!") www.codecademy.com
What does the combined comparison operator do?
The combined comparison operator is used to compare two Ruby objects. The combined comparison operator looks like this: <=>. It returns 0 if the first operand (item to be compared) equals the second, 1 if first operand is greater than the second, and -1 if the first operand is less than the second. www.codecademy.com
Create an empty hash called "foo" with a default value "bar"
foo = Hash.new("bar") www.codecademy.com
Along with false, ... is one of two non-true values in Ruby.
nil It's important to realize that false and nil are not the same thing: false means "not true," while nil is Ruby's way of saying "nothing at all." www.codecademy.com
Iterate over an array of an array. s = [["ham", "swiss"], ["turkey", "cheddar"], ["roast beef", "gruyere"]]
s.each do |x| x.each do |y| puts y end end www.codecademy.com
What happens if you try to access a key that doesn't exist, though?
A value of nil will be returned. www.codecademy.com
If we know the range of numbers, what is a much more Rubyist solution than trying to use a for loop that stops when a counter variable hits a certain value.
we can use .upto and .downto. www.codecademy.com
What is the name for this expression? boolean ? Do this if true: Do this if false puts 3 < 4 ? "3 is less than 4!" : "3 is not less than 4."
ernary conditional expression www.codecademy.com
If a method takes arguments, we say it ... or ... those arguments.
If a method takes arguments, we say it accepts or expects those arguments. www.codecademy.com
The hash syntax you've seen so far (with the => symbol between keys and values) is sometimes nicknamed the ... style.
hash rocket This is because the => looks like a tiny rocket! www.codecademy.com
Passing a block to a method is a great way of ... certain tasks from the method and defining those tasks when we call the method.
abstracting www.codecademy.com
Rewrite the hash using the new syntax. movies = { :primer => "Awesome", :memento => "Not as good the 2nd time" }
movies = { primer: "Awesome", memento: "Not as good the 2nd time" } www.codecademy.com
Symbols must be valid Ruby variable names, so the first character after the colon has to be a l... or ... ; after that, any combination of letters, numbers, and underscores is allowed.
letter or underscore (_) www.codecademy.com
Which methods to check if the variable is odd or even?
.odd? and even? www.codecademy.com
What does CRUD stand for?
C = Create R = Read U = Update D = Delete www.codecademy.com
The ... , which is the code block that describes the procedures the method carries out. The body is indented two spaces by convention (as with for, if, els if, and else statements)
body www.codecademy.com
Use a .upto to print out a range of values, from 95 up to 100.
95.upto(100) { |num| print num, " " } # Prints 95 96 97 98 99 100 www.codecademy.com
fill in the blanks case language ... "JS" puts "Websites!" ... "Python" puts "Science!" ... "Ruby" puts "Web apps!" ... puts "I don'
case language when "JS" puts "Websites!" when "Python" puts "Science!" when "Ruby" puts "Web apps!" else puts "I don't know!" end www.codecademy.com
Are symbols a string?
No t's important to remember that symbols aren't strings: "string" == :string # false www.codecademy.com
Write a case statement in a more compact way. case language when "JS" puts "Websites!" when "Python" puts "Science!" when "Ruby" puts "Web apps!" else puts "I don't know!" end
case language when "JS" then puts "Websites!" when "Python" then puts "Science!" when "Ruby" then puts "Web apps!" else puts "I don't know!" end www.codecademy.com
print the whole alphabet using the .upto method
"A".upto("Z") do |letter| puts letter end www.codecademy.com
strings = ["HTML", "CSS", "JavaScript", "Python", "Ruby"] Create a new array, symbols. Use .each to iterate over the strings array and convert each string to a symbol, adding those symbols to symbols. Tip: use the .push method
strings = ["HTML", "CSS", "JavaScript", "Python", "Ruby"] # Add your code below! symbols = [] strings.each do |x| symbols.push(x.to_sym) end www.codecademy.com
Symbols are immutable, meaning they a: can't be changed once they're created; b: can be changed once they're created;
b www.codecademy.com
A block that is passed into the sort method must return either 1, 0, -1. It should return -1 if the first block parameter should come before the second, 1 if vice versa, and 0 if they are of equal weight, meaning one does not come before the other (i.e. if two values are equal).
Fix this card ASAP www.codecademy.com
What is the difference between .to_sym and .intern
.intern, while performing precisely the same task, stresses the fact that it gets you the "internal representation" of the string - because Ruby converts all the string literals that you use in the code to symbols internally. www.codecademy.com
Rewrite this statement in a shorter way. if true puts "it is true!" end
puts "it is true!" if true www.codecademy.com
Given an literal array my_array = ["foo", "bar", "goo"] my_hash = Hash.new(0) Populate the hash with values of the array as keys, and one for each value of the array.
my_array = ["foo", "bar", "goo"] my_hash = Hash.new(0) my_array.each do | x | my_hash[x] += 1 end www.codecademy.com
What is opposite of the if statement?
The unless statement www.codecademy.com
What is a splat argument?
Splat arguments are arguments preceded by a *, which signals to Ruby: "Hey Ruby, I don't know how many arguments there are about to be, but it could be more than one." www.codecademy.com
Is there a difference between the output of the two methods? def add(a,b) return a + b end def add(a,b) a + b end
nope Ruby's methods will return the result of the last evaluated expression.This is called implicid return www.codecademy.com
Let's get a little inventive. Write a loop that only puts the even values of my_array. (Bonus points if you use a one-line if!) my_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
my_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] my_array.each do |x| puts x if x.even? end www.codecademy.com
Which method would you use in order to conver a string to an integer?
.to_i www.codecademy.com
Is hash like this valid? hash = { "bar" => 1 "bar" => 2 }
No, the keys must be unique www.codecademy.com
How can you delete movie Leon from the movie hash? movies = { Leon: 5, Horsey: 3, Pulpfiction: 5 } puts "Please enter title movie" title = gets.chomp.upcase ...
movies = { Leon: 5, Horsey: 3, Pulpfiction: 5 } puts "Please enter title movie" title = gets.chomp.upcase ... movies.delete(title) www.codecademy.com
What does the .push method do?
It adds an element to the end of an array. www.codecademy.com
What method would you use in order convert a string to a symbol?
.to_sym www.codecademy.com
What is the output of this array? my_array = [5, 6, 2, 1].sort!
[1, 2, 5, 6] www.codecademy.com
What methods would you use in order to iterate over just keys or just values?
.each_key and .each_value my_hash.each_key { |k| print k, " " } my_hash.each_value { |v| print v, " " } www.codecademy.com
What is the difference between an argument and a parameter?
The argument is the piece of code you actually put between the method's parentheses when you call it, and the parameter is the name you put between the method's parentheses when you define it. www.codecademy.com
Sort books in descending order. books = ["Charlie and the Chocolate Factory", "War an d Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]
books = ["Charlie and the Chocolate Factory", "War an d Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"] books.sort! { |firstBook, secondBook| secondBook <=> firstBook} www.codecademy.com
How can sort o string with the greatest value to be on top? frequencies = { "foo" => 1 "bar" => 2 "goo" => 3 }
frequencies = frequencies.sort_by {|a, b| b} frequencies.reverse! or frequencies = frequencies.sort_by do |foo, count| count end frequencies.reverse! www.codecademy.com
Sort books in ascending order. books = [ "Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time" ]
books = ["Charlie and the Chocolate Factory", "War an d Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"] books.sort! { |firstBook, secondBook| firstBook <=> secondBook } www.codecademy.com
The ..., which includes the def keyword, the name of the method, and any arguments the method takes.
header www.codecademy.com
What is another name for the combined comparison?
spaship operator www.codecademy.com
What does the conditional assignment operator do? ||=
It will only assign a variable if it hasn't already been assigned. In other word if the value of the variable equals to nil. www.codecademy.com
What does the .to_s method do? puts word + " " + value.to_s
Converts value to string. www.codecademy.com
Which keyword do you have to use in order to define a method?
def www.codecademy.com
What does return do?
The return keyword handles the method's output. The method won't print anything out, but it will hand us back the result of our computation. www.codecademy.com
Define a method called "doit" with two parameters "foo" and "bar". Set second parameter "bar" to false as default.
def doit(foo, bar=false) # do something end www.codecademy.com
What does the .select method do?
The .select method takes a block consisting of a key/value pair and an expression for selecting matching keys and values. grades = { alice: 100, bob: 92, chris: 95, dave: 97 } grades.select { |k,v| k > :c } # ==> {:chris=>95, :dave=>97} grades.select { |k,v| v < 97 } # ==> {:bob=>92, :chris=>95} www.codecademy.com
Section 3
(50 cards)