Ruby_catch_all

Question 1

What do programmers call the exclamation point (!)?

Answer 1

The bang operator

Question 2

What does the (!) bang operator do?

Answer 2

It reverses the value.

Question 3

What is a method?

Answer 3

A method is simply a definition of an action that can be performed on an object, i.e. like the .capitalize (method) that capitalizes text.

Question 4

What are Arguments?

Answer 4

Arguments are pieces of information that are sent to a method to be modified or used to return a specific result.

We “pass” arguments to a method when we call it.

We put arguments into the parentheses following a method. For example, 1.+(2).

Question 5

What are Parameters used for?

Answer 5

Parameters are used when you have data outside of a method’s scope, but you need access to it within the method’s scope.

def say(words)
puts words
end

You’ll notice that there’s a (words) after say in the method definition. This is what’s called a parameter.

Question 6

Argument?

Answer 6

Additional information that is provided to a method when it is called. We put arguments into the parentheses following a method. For example, 1.+(2).

Question 7

String concatenation?

Answer 7

string concatenation: Combining two strings together; accomplished with the concat() method or the + operator. Example: “zig” + “zag” returns “zigzag”.

Question 8

Objects?

Answer 8

In Ruby, and most other programming languages, we call things objects .

Question 9

Methods?

Answer 9

In Ruby, and most other programming languages, we call things objects and the actions you can tell those things to do methods.

Question 10

Class?

Answer 10

I’ve been saying for a bit that there are different “types” of objects, but in Ruby, the real word is class. 2.3 is of the class Float; 2 is of the class Fixnum (for fixed number - a number without a decimal); and Strings like “hello!” are of the class String.

Question 11

Instance?

Answer 11

Here’s another term to get familiar with: instance. Every object is an instance of a class. 2.3 is an instance of the Float class; 2 is an instance of Fixnum; and “hello!” is an instance of String. If there were a class called Person then you could have instances of it called mary, bob, and sam - they are all people because they belong to the class Person, but they are instances of the class because they are specific people. You can always see what class an object is by calling the class() method on it:

Question 12

Variables

Answer 12

Variables store objects and you can think of them like a box with a special label that can hold one thing at a time, but you can change whatever is inside that box.

Question 13

What is the receiver called when dealing with methods?

Answer 13

The object on which a method is called. Remember that the object receives the action of the method. Some methods permanently change the receiver and some do not. The String#upcase method does not change the receiver, but the String#upcase! method does.

Question 14

return value:

Answer 14

return value: The object that is returned by the method after it has run; what we see in IRB after the method is executed.

Question 15

bang

Answer 15

bang: The name of the exclamation point found at the end of Ruby methods that change the receiver when they are run.

Question 16

What are parameters

Answer 16

Parameters are used when you have data outside of a method’s scope, but you need access to it within the method’s scope. If the method does not need access to any outside data, you do not need to define any parameters.

Question 17

Get the value of key b in the following hash.

h = {a:1, b:2, c:3, d:4}

Answer 17

h[:b]

or

h.fetch(:b)

Question 18

Add to this hash the key:value pair {e:5} in the following hash.

h = {a:1, b:2, c:3, d:4}

Answer 18

h[:e] = 5

Question 19

How do you move information out of an array, given the following array, output the email from the contact_data array.

contact_data =
[[“joe@email.com”, “123 Main st.”, “555-123-4567”],
[“sally@email.com”, “404 Not Found Dr.”, “123-234-3454”]]

Answer 19

contact_data[0][0]
contact_data[1][0]

this happens because the contact_data array is a nested array, there are 2 arrays here.. So contact_data[0] pulls the first array, and then the second [0] pulls the 1st value of first array like so => contact_data[0][0], contact_data[1][0]

this outputs :
=> “joe@email.com”
=> “sally@email.com”

Question 20

Given the following data structures. Write a program that moves the information from the array into the empty hash that applies to the correct person.

contact_data =
[[“joe@email.com”, “123 Main st.”, “555-123-4567”],
[“sally@email.com”, “404 Not Found Dr.”, “123-234-3454”]]

contacts = {“Joe Smith” => {}, “Sally Johnson” => {}}

Answer 20

contacts[“Joe Smith”][:email] = contact_data[0][0]
contacts[“Joe Smith”][:address] = contact_data[0][1]
contacts[“Joe Smith”][:phone] = contact_data[0][2]

contacts[“Sally Johnson”][:email] = contact_data[1][0]
contacts[“Sally Johnson”][:address] = contact_data[1][1]
contacts[“Sally Johnson”][:phone] = contact_data[1][2]

Question 21

What does shift method do?

array = [1, 2, 3, 4]

Answer 21

it removes the first item of an array and actually
permanently removes the item.

array = [1, 2, 3, 4]
array.shift

returns
=> 1

Question 22

Use Ruby’s Array method delete_if and String method start_with? to delete all of the words that begin with an “s” in the following array.

arr = [‘snow’, ‘winter’, ‘ice’, ‘slippery’, ‘salted roads’, ‘white trees’]

Answer 22

First use the delete_if method to iterate the array, then use the start_with? method to pull the keys out that start with ‘s’.

arr = [‘snow’, ‘winter’, ‘ice’, ‘slippery’, ‘salted roads’, ‘white trees’]

arr.delete_if do |key|
key.start_with?(‘s’)
end

Question 23

take the following array and turn it into a new array that consists of strings containing one word.

a = [‘white snow’, ‘winter wonderland’, ‘melting ice’,
‘slippery sidewalk’, ‘salted roads’, ‘white trees’]

(ex. [“white snow”, etc…] → [“white”, “snow”, etc…]. Look into using Array’s map and flatten methods, as well as String’s split method.

Answer 23

a = [‘white snow’, ‘winter wonderland’, ‘melting ice’,
‘slippery sidewalk’, ‘salted roads’, ‘white trees’]

words_split = a.map do |word|
word.split
end
p words_split.flatten

THis only work if you make a new variable = to a.map.

Question 24

What are objects?

Answer 24

In Ruby, and most other programming languages, we call things objects

Question 25

What is a way to create and new hash using the new hash method?

Answer 25

Hash.new

ex. dictionary = Hash.new()
returns
=> {}

Question 26

What is a conditional?

Answer 26

A conditional is a fork (or many forks) in the road.

Question 27

Add ages for Marilyn and Spot to the existing hash. ages = { “Herman” => 32, “Lily” => 30, “Grandpa” => 5843, “Eddie” => 10 }; additional_ages = { “Marilyn” => 22, “Spot” => 237 }

Answer 27

ages.merge!(additional_ages)