ruby

Question 1

attr_accessorattr_readerattr_writer

Answer 1

A = B + C

Question 2

What’s ARGV short for?

Answer 2

Argument vector, 紧跟在ex01.rb后面的参数比如，ARGV.first就是第一个参数

Question 3

Difference puts/print?

Answer 3

1. puts print new line2. puts ignore nil when displaying arrays

Question 4

Difference: gets, STDIN.gets, STDIN.gets.chomp()

Answer 4

STDIN.gets.chomp() reads user input first;gets.chomp() reads ARGV first;.chomp() removes the /n at the end of the string.

Question 5

default name of script?

Answer 5

$0

Question 6

why close files?

Answer 6

to save some memory, or it’ll have to wait until garbage collection, which could come at who knows when

Question 7

how to read/write a file?

Answer 7

File.open(from_file).read()File.open(to_file, “w”).write(content)

Question 8

how to take more than one parameter?

Answer 8

use asterisk:def a_function (*args) print args # an arrayend

Question 9

can we do maths inside of the parenthesis?

Answer 9

yes

Question 10

how to reset read progress (rewind)?how to readlines?

Answer 10

input_file.seek(0, IO::SEEK_SET)input_file.readline()

Question 11

a, b, c = [1, 2, 3, 4]

Answer 11

a => 1b => 2c => 3

Question 12

how to require modules in irb?module Ex25 def self.break_words(stuff) words = stuff.split(‘ ‘) words endend

Answer 12

require ‘./ex25’Ex25.break_words(sentence)

Question 13

how to generate [1, 2, 3, 4, 5]?

Answer 13

Array(1..5)(1..5).to_a

Question 14

Range:(-1..-3).to_a(-3..-1).to_a(‘a’..’c’).to_a(‘a’…‘c’).to_a

Answer 14

[][-3, -2, -1][‘a’, ‘b’, ‘c’][‘a’, ‘b’]

Question 15

how to cycle through an array?

Answer 15

a.cycle { |x| puts x } # goes on forevera.cycle(2) { |x| puts x } # execute twice

Question 16

how to print the index/item of an array?

Answer 16

a.each_index { |x| puts x }a.each { |x| puts x }

Question 17

first and last item of an array?

Answer 17

array.firstarray.last, array[-1]

Question 18

take a part of an array (index 3 to 5), and join them into a string separated by “#”?

Answer 18

array.values_at(3, 5).join(“#”)

Question 19

the opposite of if?

Answer 19

unless

Question 20

the opposite of while?

Answer 20

until

Question 21

print “Odelay!” 5 times

Answer 21

5.times { print “Odelay!” }

Question 22

what’s the difference between symbols and strings?

Answer 22

you want to use strings for data, for things that you might want to truncate, turn to uppercase, or concatenate. Use symbols when you simply want an intelligible thing that stands for something in your code.e.g.person = {}person[:name] = ‘russ’puts “Name: #{person[:name]}”notputs “Name: #{person[‘name’]}”

Question 23

difference: $x, @y @@z

Answer 23

Variables which begin with a dollar sign are global.Variables which begin with an at symbol are instance variables.Variables which begin with double at symbols are class variables. Think of the double at prefix as meaning attribute all. Additionally, you can think of a swarm of AT-ATs from Star Wars, which are all commanded by Ruby. You change a class variable and not just one changes, they all change.

Question 24

Regular expression!

Answer 24

A regular expression (or regexp) is a set of characters surrounded by slashes./ruby/, /[0-9]+/ and /^\d{3}-\d{3}-\d{4}/ are examples.Regular expressions are used to find words or patterns in text. The slashes on each side of the expression are pins.Imagine if you had a little word with pins on both side and you held it over a book. You pass the word over the book and when it gets near a matching word, it starts blinking. You pin the regular expression onto the book, right over the match and it glows with the letters of the matching word.Oh, and when you poke the pins into the book, the paper sneezes, reg-exp!Regular expressions are much faster than passing your hand over pages of a book. Ruby can use a regular expression to search volumes of books very quickly.