Object Types Flashcards
To find information on objects, classes, methods, etc… Where would you find these answers?
www.ruby-doc.org/core/
To find information on a method within Ruby, what command do you issue in Ruby to find more information?
ri object name
for example ri upcase
or
.inspect shows human readable form
True of False:
Variables are objects?
False
However, once a variable is defined, it will act like an object
What does this error code mean?
NameError: undefined local variable or method `x’ for main:Object
It means you have not defined your variable, in this case, the variable ‘x’
Variables should be named in what format?
lower case with underscores
for example: articles_written = 100
The scope indicator of the Global scope is what?
Dollar sign
example: $variable
The scope indicator of the Class scope is what?
Two at symbols
example: @@variable
The scope indicator of the Instance scope is what?
The at symbol
example: @variable
The scope indicator of the Local scope is what?
nothing, just the variable name
example: variable
The scope indicator of the Block scope is what?
nothing, just the variable name
example: variable
Ruby separates integers in two categories, what are they?
> integers
> floats
If integers are objects, what two subclasses must they belong to?
Fixnum and Bignum
examples:
1234. class => Fixnum
12345678. class => Bignum
What would the result be in Ruby?
-200.abs
=> 200
Since .abs returns the absolute value
What would the result be in Ruby?
200.next
=> 201
Since .next returns the next value
Floats or Floating point numbers are also known as what?
decimal numbers or precision numbers
x = 10 y = 10.0
what would x and y equal in Ruby?
10.0
10 / 3 in Ruby would return what value?
3
10.0 / 3.0 in Ruby would return what?
3.33333333333333
If you wanted to round this number, what would you enter in Ruby?
12345.6789
12345.6789.round
=> 12346
If you wanted to make this number an integer, what would you enter in Ruby?
12345.6789
12345.6789.to_i
=> 12345
If you wanted to round this number UP, what would you enter in Ruby?
12345.6789
12345.6789.floor
=> 12345
If you wanted to round this number DOWN, what would you enter in Ruby?
12345.6789
12345.6789.ceil
=> 12346
strings are a sequence of what?
characters
what does this return in irb?
“Lamda”*3
“LamdaLamdaLamda”
Which character lets you escape a quote?
\
also known as a backslash
What does this yield?
greeting = “hello”
target = “world”
puts “I want to say #{greeting} #{target}.”
I want to say hello world.
What method makes a string backward?
.reverse
example: “Hello”.revers
=> “olleH”
What method makes a string capitalized?
.capitalize
example: “hello”.capitalize
=> “Hello”
What method makes a string all lower cased?
.downcase
example: “Hello”.downcase
=> “hello”
What method makes a string all upper cased?
.upcase
example: “Hello”.upcase
=> “HELLO”
If you wanted to count how many letters there were in the string “Hello”, what would you enter?
“Hello”.length
=> 5
Take “hello” and reverse it, make it all upper case, and count the letters
“Hello”.reverse.upcase.length
=> 5
Define an array.
An ORDERED INTEGER-INDEXED collection of OBJECTS
Name 4 things that can go in an array
- Strings
- Numbers
- Other arrays
- Mixed Types
Enter what to make an empty array called master_array
master_array = []
put the letters a, b, and c in an array named my_first_letters
my_first_letters = [“a”, “b”, “c”]
given this array:
my_first_letters = [“a”, “b”, “c”]
what would this return:
my_first_letters[1]
“b”
given this array:
my_first_pets = [“dog”, “pig”, “cat”]
what would you enter to turn “cat” into “goat”
my_first_pets[2] = “goat”
to clear out an array, what method would you use?
my_array.clear
if you wanted to append “goat” onto the array my_first_pets = [“dog”, “pig”, “cat”]
what would you enter?
my_first_pets «_space;“goat”
Given this array:
my_first_pets = [“dog”, “pig”, “cat”, “goat”, “cat”, “dog”]
What would you enter to get an array containing only one type of animal (no duplicates)
my_first_pets.uniq
Given this array:
my_first_pets = [“dog”, “pig”, “cat”, “goat”, “dog”]
What would you enter to get an array containing only dogs and pigs?
my_first_pets.delete_at(2)
=> [“dog”, “pig”, “goat”, “dog”]
Define hashes
UNORDERED collection of objects connected by KEY-VALUE PAIRS
Make a hash named my_hash
my_hash = {}
Make a hash named my_hash with the key value pairs of ‘first item’ and ‘bong’
my_hash = {“first_item”=>”bong”}
Given this hash>
name = {“first_name” => “Roberto”, “last_name”=>”Sanchez”}
how would you get the first name out?
name[“first_name”]
Given this hash>
name = {“first_name” => “Roberto”, “last_name”=>”Sanchez”}
What would this return?
name.index(“Sanchez”)
=> “last_name”
create a symbol named after your test project
:test_project
create a hash with two symbols for first and last names
name = {:first_name => “Roberto”, :last_name => “Sanchez”}
Define a boolean
something that is either True or False
What is the comparison & logic operator for ‘equal’?
==
What is the comparison & logic operator for ‘less than or equal to’?
<=
What is the comparison & logic operator for ‘Not’?
!
What is the comparison & logic operator for ‘Not equal’?
!=
What is the comparison & logic operator for ‘and’?
&&
What is the comparison & logic operator for ‘or’?
||
