Begging Ruby Chapter 1 Flashcards by Ari Ingber

What is object orientation

everything is an object guitar amps studio

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Data Types

variable can hold these

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Control Structures

variable can hold these

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Is Ruby Open Source?

Yes

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Ruby Interpreter

This is a ruby program that understands other programs written in the Ruby language, along with a collection of extensions and libraries to make your Ruby more fully featured

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irb: Interactive Ruby

irb stands for “Interactive Ruby.” “Interactive” means that as soon as you type something, your computer will immediately attempt to process it. Sometimes this sort of environment is called an immediate or interactive environment.

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object-oriented programming language

In the simplest sense, this means that your Ruby programs can define and operate upon concepts in a real-world fashion. Your program can contain concepts such as “people,” “boxes,” “tickets,” “maps,” or any other concept you want to work with. Object-oriented languages make it easy to implement these concepts in
a way that you can create objects based upon them. Object oriented languages can then act upon and understand the relationships between these concepts in any way you define.

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nouns / verbs

Objects are nouns, methods are verbs.

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3 corners of OOP

Encapsulation, Inheritance, Polymorphism

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OOP

Style of programming where you create representations of “types” of objects like guitars and amps (Classes), and then can create specific objects like 69 strat, black les paul, 80s peavey, (instance of an object) that intend to use with each other.

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attr_accessor

attr stands for “attribute,” and accessor roughly means “make these attributes accessible to be set and changed at will.”

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print vs puts

puts automatically moves the output cursor to the next line

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what can a ruby variable contain

numbers, text, and other data structures

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class

A class is the definition of a single type of object

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standard attribute syntax

attr_accessor :name, :age, :gender

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what does inheritance allow you to do

Inheritance allows different classes to relate to one another and group concepts by their similarities

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classless method

def guitar_strum
puts “brrriiing”
end

guitar_strum

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Class

Class: A class is a definition of a concept in an object-oriented language such as Ruby. We created classes called Pet, Dog, Cat, Snake, and Person. Classes can inherit features from other classes, but still have unique features of their own.

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Method

Method: A method represents a set of code (containing multiple commands and statements) within a class and/or an object. For example, our Dog class objects had a bark method that printed “Woof!” to the screen. Methods can also be directly linked to classes, as with fred = Person.new, where new is a method that creates a new object based upon the Person class. Methods can also accept data—known as arguments or parameters—included in parentheses after the method name, as with puts(“Test”).

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Arguments/parameters

Arguments/parameters: These are the data passed to methods in parentheses (or, as
in some cases, following the method name without parentheses, as in puts “Test”). Technically, you pass arguments to methods, and methods receive parameters, but for pragmatic purposes, the terms are interchangeable.

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Kernel

Some methods don’t require a class name to be usable, such as puts. These
are usually built-in, common methods that don’t have an obvious connection to any classes. Many of these methods are included in Ruby’s Kernel module, a module that provides functions that work from anywhere within Ruby code without being explicitly referred to.

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Experimentation

One of the most fulfilling things about programming is that you can turn your dreams into reality. The amount of skill you need varies with your dreams, but generally if you want to develop a certain type of application or service, you can give it a try. Most software comes from necessity or a dream, so keeping your eyes and ears open for things you might want to develop is important. It’s even more important when you first get practical knowledge of a new language, as you are while reading this book. If an idea crosses your mind, break it down into the smallest components that you can represent as Ruby classes and see if you can put together the building blocks with the Ruby you’ve learned so far. Your programming skills can only improve with practice.

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simple do if syntax

age = 10

puts “You’re too young to use this system” if age

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string literal

When a string is embedded directly into code, using quotation marks as earlier, the con- struction is called a string literal. This differs from a string whose data comes from a remote source, such as a user typing in text, a file, or the Internet. Any text that’s pre-embedded within a program is a string literal.

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interpolation

interpolation refers to the process of inserting the result of an expression into a string literal "#{x+y}"

"Test" + "Test"

TestTest

"Test".capitalize

Test

"Test".downcase

test

"Test".chop

Tes

"Test".next

Tesu

"Test".reverse

tseT

"Test".sum

416

"Test".swapcase

tEST

"Test".upcase

TEST

"Test".upcase.reverse

TSET

"Test".upcase.reverse.next

TSEU

regular expression (string)

A regular expression, therefore, is a string that describes a pattern for matching elements in other strings.

basic substitution

puts "yo la tango".sub('tango', 'mango')

regular expression

puts "foobar".sub('bar', 'foo')

regular expression substitution of first two characters syntax

x.sub(/^../, 'Hello')

iterate through a string and have access to each section of it separately

"xyz".scan (/./) { |character| puts character }

any alphanumeric character or an underscore

regular expression argument general syntax

(/something/)

Anchor for the beginning of a line

Anchor for the end of a line

Anchor for the start of a string

Anchor for the end of a string

Any character

Any letter, digit, or underscore

Anything that \w doesn’t match

Any digit

Anything that \d doesn’t match (non-digits)

Whitespace (spaces, tabs, newlines, and so on)

Non-whitespace (any visible character)

scanning for each character but adding them together to make a word

.scan (/.+/)

scan for vowels syntax

"This is a test".scan(/[aeiou]/) { |x| puts x }

matching operator

array to string syntax

x.join(' ')

turning a string into an array syntax

"Words with lots of spaces".split(/\s+/)

basic hash iteration syntax

x.each { |key, value| something happens here with each }

ternary operator

2 > 1 ? "yes" : "no"

ternary syntax

2 > 1 ? "yes" : "no"

x y

Comparison; returns 0 if x and y are equal, 1 if x is higher, and -1 if y is higher

turn beginning two elements of array into string with dash

array.first(2).join("-")

discarding hash elements

x.delete(key)

discard hash conditional example

hash_name.delete_if { |key, value| value

fruit case example

``` fruit = "orange" color = case fruit when "orange" "orange" when "apple" "green" when "banana" "yellow" else "unknown" end ```

code block

essentially an anonymous, nameless method or function | [{} or do end]

how to turn letters a through z into an array

('A'..'Z').to_a

hash basic syntax

s = { :key => 'value' }

Variable

A placeholder that can hold an object—from numbers, to text, to arrays, to objects of your own creation.

Operator

Something that’s used in an expression to manipulate objects such as +(plus), - (minus), * (multiply), and / (divide). You can also use operators to do comparisons, such as with , and &&.

Integer

A whole number, such as 5 or 923737.

Float

A number with a decimal portion, such as 1.0 or 3.141592.

Character

A single letter, digit, unit of space, or typographic symbol.

String

A collection of characters such as Hello, world! or Ruby is cool.

Constant

A variable with a fixed value. Constant variable names begin with a capital letter.

Iterator

A special method such as each, upto, or times that steps through a list element by element. This process is called iteration, and each, upto, and times are iterator methods.

Interpolation

The mixing of expressions into strings.

Array

A collection of objects or values with a defined, regular order.

• Hash

A collection of objects or values associated with keys. A key can be used to find its respective value inside a hash, but items inside a hash have no specific order. It’s a lookup table, much like the index of a book or a dictionary.

Regular expression

A way to describe patterns in text that can be matched and compared against.

Flow control

The process of managing which sections of code to execute based on certain conditions and states.

Code block

A section of code, often used as an argument to an iterator method, that has no discrete name and that is not a method itself, but that can be called and handled by a method that receives it as an argument. Code blocks can also be stored in variables as objects of the Proc class (or as lambdas).

Range

The representation for an entire range of values between a start point and an endpoint.

Symbol

A unique reference defined by a string prefixed with a colon (for example, :blue or :name). Symbols don’t contain values as variables do, but can be used to maintain a consistent reference within code. They can be considered as identifiers or constants that stand alone in what they abstractly represent.

. .

including

. . .

not including

how would you check if letters a through z has r in it

('a'..'z').include?('r')

create a new triangle

Triangle.new(1,2,3)

what is the benefit of inheritence?

classes lower down the hierarchy get the features of those higher up, but can also add specific features of their own

what is the escape charecter

backslash \

print first 3 letters of "string"

p "string"[0..2]

how to create a lambda

l = lambda { "Do or do not" } | puts l.call

increase of all menu items by 10%

menu_items = {:curry => 4, :roti => 6} menu_items.each do |item, price| menu_times[item] = price * 1.1 end

.count

.count(argument) goes through an array and counts how many time argument appears

Select random elements from an array

def random_select(array, n) result = [] n.times do result

newest hash syntax

{ k: v }

how to spell initialize

Init i alize

summing elements in an array

inject(0) { |sum, num| sum + num }

syntax for simple do if w/ two conditionals

do if condition1 == true && condition2 == true

do using unless

do unless conditional1==true

not equal to comparison operator

how to loop from n to m

n.upto(m) { code to loop }

how to code loop from m down to n

m.downto(n) { code to loop }

0 to 50 in 5 steps

0.step(50, 5) { code to loop }

using string delimiters

x =

result of "abc" * 5

abcabcabcabcabc

basic interpolation

"#{something}"

define regular expression

a search query

how to iterate through a string

'string'.scan(/./){ |char| do something }

returning a string with no spaces

"this is a crazy sentence 123".scan(/\S+/).join

matching operator

.scan vs .match

.scan goes though everything, . match returns one match value

method to check if array has no elements

array.empty?

does an array have an element

array.include?(ImptArrgument)

methods for array and hash

``` .delete .delete_if .first .collect .each ```

methods for array

``` .first .first(arg) .last .last(arg) .reverse ```

hash methods

``` .size .each .keys .values .delete .delete_if .first ```

how to create a new hash which saves changed old hash

new_hash = {}; old_hash.each { |key,val| new_hash[key] = val + something }

demonstration of a class method

``` class Thing def self.thing_method puts "hello from class method" end ```

%w{ this is a long sentence }

[ "this", "is", "a", "long", "sentence" ]

%q{ this is a long sentence }

" this is a long sentence "

.collect

Returns a new array with the results of running block once for every element in enum.

Begging Ruby Chapter 1 Flashcards

(124 cards)