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Question 1

What is a method?

Answer 1

A block of code referred to by name.

Question 2

What’s the difference between a method and a function?

Answer 2

A method is associated with an object.

A function stands alone.

Question 3

Does ruby have functions? Why or why not?

Answer 3

Not strictly. All functions in ruby are actually methods as they are all associated with an object.

Question 4

In regards to a method, what is meant by its “side effects” ? What is a commonly used function with a side effect?

Answer 4

A side effect is some sort of modification to a non-local variable or some sort of observable interaction with the outside world.

Example: puts

Question 5

What is an implicit return? Is this preferred? Why or why not?

Answer 5

The last evaluated expression in a method is the return value of that method.

Question 6

What are three signs of a good method?

Answer 6

It does one thing.

It has a short description and a good name.

It’s body is under 10 lines long.

Question 7

How many lines should a method be limited to?

Answer 7

10

Question 8

What is an object?

Answer 8

A convenient way of grouping data and behavior.

Question 9

Data and behavior is grouped together within a..

Answer 9

object

Question 10

What in ruby is not an object?

Answer 10

Trick question: everything is an object.

Question 11

What is the parent class for all objects in Ruby?

Answer 11

Object

Question 12

Describe Object’s relation to other classes in Ruby.

Answer 12

Object is the parent class for all other classes.

Question 13

What’s the difference between calling puts and p on an object?

Answer 13

puts returns object.to_s

p returns object.inspect

Question 14

Why does nil.nil? return true?

Answer 14

Object#nil?

returns false, while only NilClass#nil? returns true

Question 15

How do you test to see if an object is an instance of a particular class?

Answer 15

Object#is_a?

Question 16

What module is mixed into every class?

Answer 16

Kernel

Question 17

Why are methods like puts and gets available to any context?

Answer 17

The Kernel module is mixed into every class.

Question 18

Array#each is a bad way to delete elements within an array. What’s a better method?

Answer 18

Array#delete_if

Question 19

How do we tell if an array has 0 elements?

Answer 19

Array#empty?

Question 20

What two methods are used when treating an Array as a Queue?

Answer 20

Array#push

Array#shift

Question 21

What’s a naming technique that helps the user known that a variable is an array?

Answer 21

Make it plural.

Question 22

Why is an array variable name typically pluralized?

Answer 22

To help the user know that the variable represents an array.

Question 23

Why not mix types in an array?

Answer 23

It makes it difficult to iterate when the type of the item changes.

Question 24

Why is string interpolation preferred over concatenation?

Answer 24

It’s easier to read.

Question 25

str = “asdfjkl”

What’s a way to access the substring “dfj” of str using only the bracket operator?

Answer 25

str[2,3]

Question 26

How do you replace all instances of a pattern within a string?

Answer 26

String#gsub

Question 27

How do you set up multiple replacements within a single call to String#gsub?

Answer 27

pass it a hash where the keys are the matches and the values are the replacements.

Question 28

How do you convert a semi-string, i.e. “123 Flatbush” into an integer? What will it return in this example?

Answer 28

String#to_i

123

Question 29

What’s the purpose of String#to_sym?

Answer 29

Return a symbol that points to the string.

Question 30

What does nil.to_s return?

Answer 30

”” (empty string)

Question 31

What’s the difference between:

bundle exec rspec
rspec

Answer 31

The first changes PATH to the local directory. This causes the local RSpec version to be used.

The second uses the system’s version of RSpec, which may be out of date or incompatible with the spec’s.

Question 32

Rule of thumb: how much longer does it take to debug than to write code?

Answer 32

10x

Question 33

What’s the term for an input that produces the wrong output?

Answer 33

a regression

Question 34

How do you step into a method call in byebug?

Answer 34

step

Question 35

How do you step out of a method call in byebug?

Answer 35

finish

Question 36

What are two cases where a NameError might be thrown? What are their error messages? When are they each thrown?

Answer 36

NameError: undefined local variable – thrown when using a variable or method that hasn’t been defined

NameError: uninitialized constant – thrown when a class or other constant is referenced but cannot be found.

Question 37

when using a variable or method that hasn’t been defined, what Exception will be thrown, and with what error message?

Answer 37

NameError: undefined local variable

Question 38

when using a Class that can’t be found by the interpreter, what Exception will be thrown, and with what error message?

Answer 38

NameError: uninitialized constant

Question 39

When might a NoMethodError be thrown?

Answer 39

when it’s clear that the user tried to call a method (not a variable) that doesn’t exist.

Question 40

when it’s clear that the user tried to call a method (not a variable) that doesn’t exist., what error is thrown?

Answer 40

NoMethodError

Question 41

If we don’t give a method the right number of arguments, what exception will be thrown at us? What error message?

Answer 41

ArgumentError: wrong number of arguments

Question 42

When might a TypeError be thrown? What’s a typical error message?

Answer 42

if you pass the wrong type of thing to a method.

TypeError: String can’t be coerced into Fixnum

Question 43

if you pass the wrong type of thing to a method, what error is thrown? What error message?

Answer 43

TypeError: can’t be coerced into

Question 44

What are two cases where a LoadError might be thrown? What’s a typical error message?

Answer 44

LoadError: cannot load such file –

This can happen when you’re requiring a gem that hasn’t been installed.

This can also happen when you’re trying to require a file without using the initial “./”

Question 45

What error is thrown when you’re requiring a gem that hasn’t been installed?

Answer 45

LoadError

Question 46

What error is thrown when you’re trying to require a file without using the initial “./”

Answer 46

LoadError

Question 47

Writing ungrammatical code will throw what type of error?

Answer 47

SyntaxError

Question 48

What are 3 common causes of SyntaxErrors?

Answer 48

forgetting to close quotes

forgetting to close parentheses

forgetting to close do-end blocks

Question 49

What caused this error:

SyntaxError: /Users/ruggeri/test.rb:4: syntax error, unexpected keyword_end, expecting $end

Answer 49

An extra end statement

Question 50

What caused this error:

SyntaxError: /Users/ruggeri/test.rb:3: syntax error, unexpected $end, expecting keyword_end

Answer 50

A missing end statement

Question 51

An extra end statement will throw what error?

Answer 51

SyntaxError: /Users/ruggeri/test.rb:4: syntax error, unexpected keyword_end, expecting $end

Question 52

A missing end statement will throw what error:

Answer 52

SyntaxError: /Users/ruggeri/test.rb:3: syntax error, unexpected $end, expecting keyword_end

Question 53

How do you call a block with a single parameter ‘name’ from a method?

Answer 53

within the method, use:

yield(name)