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Justin Mui

Justin Mui

Methods: Part 2

Slide Duration:

Table of Contents

I. Introduction to Ruby
Setting Up Your Environment

22m 8s

Intro
0:00
Installing Ruby
0:06
Ruby-lan.org
0:07
Three Ways of Installing Ruby
2:26
Compiling Ruby-Source Code
3:02
Third Party Tools
3:28
Other Implementations of Ruby
4:48
Windows Installation
5:21
RubyInstaller.org
5:22
Mac OSX and Linux Installation
6:13
Mac OSX and Linux Installation
6:14
Setting Up Debian/Linux
6:42
Setting Up Debian/Linux
6:43
Installing HomeBrew
6:56
HomeBrew for MAC OSX
6:57
HomeBrew Wiki
9:44
Installing HomeBrew
10:02
Setting Up Mac OSX
11:46
HomeBrew, RVM, OSX-GCC Installer, and Install Ruby 1.9.3
11:47
Ruby Version Manager (RVM)
12:11
Ruby Version Manager (RVM) Overview
12:12
Installing Ruby Version Manager (RVM): http://rvm.io
12:35
Install RVM with Ruby
14:20
Install RVM with Ruby
14:21
Install OSX-GCC-Installer
16:18
Download and Install Package for Your OSX
16:19
Install Ruby 1.9.3
17:28
Install Ruby 1.9.3
17:29
Test It Out!
18:09
rvm-help & ruby-v
18:10
Example: rvm gemset create educator
18:52
Set It As Default!
20:47
rvm Use 1.9.3@educator--default
20:48
Intro to Ruby

22m 20s

Intro
0:00
What is Ruby?
0:06
What is Ruby?
0:07
Ruby Standard Library
0:52
Who Created Ruby?
1:22
Yukihiro Matsumoto
1:23
History
2:45
The Name 'Ruby'
2:46
Ruby v0.95
3:10
Ruby v1.0
3:56
English Language Mailing List Rubytalk
4:08
ruby-forum.com & the Mailing Lists
4:27
Ruby In The West
9:51
Ruby on Rails
10:39
The Pragmatic Programmer's Guide to Ruby
11:30
rubyonrails.org
13:34
Current Ruby
14:42
Ruby 1.8.7, Ruby 1.9.3, and Ruby 2.0
14:43
Why Programmers Enjoy Ruby?
15:40
Why Programmers Enjoy Ruby?
15:41
Ruby Is An Interpreted Language
16:21
Ruby Is An Interpreted Language
16:22
What Is It Used For?
16:50
What Is It Used For?
16:51
Ruby is Object-Oriented
18:17
Example: 5.class
18:18
Example: 0.0.class
18:54
Example: true.class
19:03
Example: nil.class
19:12
Object Class
19:19
BasicObject
19:20
Example
19:52
Superclass
20:50
Fixnum → Integer → Numeric → Object
21:32
Basic Tools for Using Ruby

27m 44s

Intro
0:00
Interactive Ruby
0:08
irb: Interactive Command-Line Environment
0:09
Example
0:49
irb-v
0:50
irb-executes terminal
1:02
1.9.3-p125 > 'hi'
1:09
Live Demonstration
1:31
Why Use Interactive Ruby?
2:21
Why Use Interactive Ruby?
2:22
RDoc
3:05
RDoc
3:06
Ruby Core Documentation
3:32
Ruby Core Documentation: Example
5:30
Ruby Core Documentation: Markup
6:12
Ruby Core Documentation: Headings
7:44
Coding Example: RDoc
9:30
Why Use RDoc?
13:02
Learning Core Ruby Functions
13:03
Generating RDoc
15:31
rdoc-help # usage
15:32
Ruby Interpreter
15:57
ruby -- help
15:58
ruby [switches] [-] program [arguments]
16:16
Example: How to Run a Ruby Script
16:28
Rake
18:38
Rake Overview
18:39
Ruby Core Documentation: Rake
19:46
Coding Example: Rake
23:14
Why Was It Created?
24:30
Why Was It Created?
24:31
Lesson Summary
25:13
Lesson Summary
25:14
IDE/script Editors: MacVIM
26:24
Ruby Specifics

20m 45s

Intro
0:00
Ruby Specifics
0:06
Comments
0:51
Hashtags
1:00
Example
1:23
Multi-Line Comment
2:04
Example
3:10
RDoc Comments
4:02
When do you generate an Rdoc?
4:10
Headings and subheadings
4:24
Examples
4:48
Generating an Rdoc - example
4:50
Common Code Conventions
6:28
For every tab use two spaces indentation
7:38
Never use tabs
7:42
Common Code Conventions (Cont.)
8:18
Camel case
8:20
Snake case
9:18
Identifiers
9:44
Constants begin with CAP letter
10:00
Examples
10:10
Identifiers with Different Scoping
10:26
Global
10:34
Instance Variable
10:40
Class Variable
10:46
Examples
10:56
Reserved Keywords
12:22
Do not use reserved keywords in code
12:25
Parentheses are Sometimes Optional
13:04
Functions do not require parentheses
13:16
When in doubt, use parentheses
13:54
Examples
14:10
Newlines Are Statement Terminators
14:20
Examples
15:10
Continuation with a Period
16:20
Period means continue to next line
16:46
Multiple Statements Allowed on a Single Line
17:38
Try not to use semi-colons
17:58
Code Blocks
18:20
Use code blocks for one liners
18:28
Examples
18:40
Recommended for multiple lines
20:16
Ruby Data Types (Part 1)

29m 37s

Intro
0:00
Overview
0:10
Ruby Data Types
0:10
Numbers
0:16
Strings
0:18
Symbols
0:24
Numbers
0:30
Numeric
0:44
Float
0:50
Complex
0:56
BigDecimal
0:58
Rational
1:00
Integer (most popular) - Fixnum and Bignum
1:06
Fixnum stores 31 bits
1:18
Bignum stores larger bits
1:24
All number objects are instances of Numeric
1:28
Integer Literals
2:28
Represent whole-numbers
2:40
Examples - Different bases
2:42
Binary
3:04
Octal
3:30
Hexadecimal
3:44
Examples
4:06
Floating Point Literals
4:45
Examples
4:58
e-value can be capital or lowercase
5:30
Example
5:44
Strings
6:16
Mutable objects
6:18
Used for inserting and deleting text, searching, and replacing
6:26
String Rdoc
6:46
Definition
7:00
String Literals
8:20
Single-Quoted
8:28
Double-Quoted (most used)
8:50
Example
9:32
Escape Sequences
11:10
Newline
11:16
Tab
11:22
Double quote
11:28
Blackslash
11:36
Interpolation
11:50
Sprintf
13:48
Unicode Escaping
14:38
Example
15:50
Delimiters
16:18
Here Documents
17:18
Example
17:25
String Operators
19:58
Concatenation
20:03
Appending
20:40
String Equality
21:04
Example
21:24
Substrings
22:00
Range object (inclusive)
22:22
String Encoding
24:52
Differences between Ruby 1.8 and 1.9
24:56
Symbols
26:02
Definitions
26:04
Examples
26:46
When to use symbols
26:54
Symbols and Strings
27:42
Symbols Rdoc
28:22
Ruby Gems

25m 50s

Intro
0:00
RubyGems
0:08
What are RubyGems?
0:24
RubyGems.org
0:44
How RubyGems are used
2:06
Java's jar utility
2:50
Unix/Linux's tar utility
3:06
What is a Gem?
3:16
Definition of Gem
3:20
Version
3:34
Date
3:44
Author
3:50
Description
5:58
What Are the Uses?
4:18
Uses for Gems
4:22
Installation
5:06
How to install RubyGems
5:30
Updating to the Latest Ruby Gems
5:54
Testing
6:22
Example
6:34
Installing Rake
7:24
Example
7:46
Verifying
9:22
Example
9:56
Structure
10:56
gem.gemspec
11:30
Specification
13:40
What is in the gem?
13:42
Who made it?
13:50
Update gem version
13:58
Example
14:10
Create Our First Gem
17:20
Steps involved
17:28
RubyGems Guides
17:36
Example
20:02
Steps Review
18:56
Create Our First Gem (Cont.)
23:08
Building the gem
19:38
Example
20:00
Installing the gem
22:32
Run it
22:52
Publish it
23:04
Get Some Gems!
25:06
rake
25:14
rails
25:19
fastercsv
25:25
koala
25:37
Ruby Data Types (Part 2)

40m 24s

Intro
0:00
Ruby Data Types
0:15
Boolean
0:21
Arrays
0:27
Hashes
0:33
Range
0:37
Boolean Types
0:42
TrueClass
0:56
FalseClass
1:12
NilClass
1:18
TrueClass Examples
2:48
FalseClass Examples
3:22
Arrays
4:16
Ordered collection of objects
4:22
Can hold different objects
4:32
Starts at index 0
4:50
Array of Strings
5:50
Example
5:52
Arrays (Cont.)
6:20
Can be created using literals
6:22
Can be created using constructors
6:54
Position and indexed value
8:04
Negative Indexed Values
8:56
Shift and Unshift
10:18
Push and Pop
11:38
.delete method
12:38
Addition and Subtraction
13:32
Union and Intersection
14:48
Insert
15:52
Iteration
16:52
Arrays Rdoc
17:48
Hashes
22:08
Maps and Associative Arrays
22:44
Created using the constructor
22:56
Created using a hash literal
24:02
Stored in a hash table
25:26
Example
25:50
Accessing Key-Values
27:46
Deletion
29:48
Iteration
31:04
Hashes Rdoc
32:04
Ranges
36:40
Two dots are inclusive
36:57
Three dots are exclusive
37:16
Example
37:50
Ranges Rdoc
38:24
Objects

1h 5m 46s

Intro
0:00
Objects
0:10
Object References
1:36
Ruby Core
2:16
Example
4:30
Creating New Objects
6:00
New Method
6:08
Initialize Method
6:31
Example
7:18
Garbage Collection
9:54
Global values always reachable
10:25
Object Identity
11:08
Every object has an object identifier
11:20
Object identifier is constant and unique
11:30
Example
11:54
Object Class
12:58
Class method
13:10
Superclass method
13:28
Object Testing
14:46
is_a?
15:49
respond_to?
16:26
String and Regexp
18:10
Comparing two object instances
20:06
Example
23:30
Object Equality
25:48
Comparing objects
25:54
equal?
25:58
Popular way to test for equality
27:16
Opposite way to test for equality
27:25
Arrays
28:30
Hash
29:42
Case equality operator
30:47
Class tests
31:16
Range tests
31:48
Symbol tests
32:32
Object Conversion
33:14
Explicit conversion
33:54
Implicit conversion
35:00
Example
36:12
Object Conversion: Kernel Module
38:22
Array
38:38
Float
39:26
Integer
39:58
String
40:10
Example
40:34
Object Conversion: Coerce
42:00
Used for mixed type numeric operations
42:08
Example
43:40
Object Conversion: Boolean
47:42
Every object has a boolean value
47:44
Example
48:54
Object Copying
50:52
dup
50:58
clone
51:03
Example
51:42
Object Freezing
57:36
Object Marshaling
58:38
Save state
59:04
Load state
59:27
Example
59:32
Tainted Objects
1:01:50
taint
1:02:08
farm field
1:02:12
Untrusted Objects
1:04:06
trust
1:04:24
untrust
1:04:34
untrusted?
1:04:42
Loops

38m 54s

Intro
0:00
Loops
0:12
while and until
0:48
for and in
0:54
iterators
1:04
enumerable in objects
1:06
While-loop
1:14
Will keep going is condition is true
1:18
Until-loop
2:58
Will keep going until condition becomes true
3:06
Single Expression Loops
4:20
Compact form
4:30
Expressed as a modifier
4:42
Do-While Loop
5:52
Executes body first
6:06
Do-Until Loop
7:54
Similar to do-while loop
7:58
Using Break Inside Loops
8:54
break
8:58
For-In Loop
11:56
for-loop
12:06
var
12:34
collection
12:54
body
13:00
Examples
13:08
Examples (Cont.)
15:54
Nested loops
16:40
Numeric Iterators
18:32
upto
18:40
downto
18:42
times
18:48
Examples
20:28
External Iterators
21:00
Enumerator class
21:04
Rdoc
21:16
Enumerables in Objects
24:35
Enumerable is a mix-in
24:41
RDoc
25:24
Commonly Used Enumerables in Objects
27:01
Array
27:19
Hash
27:51
Range
28:47
Examples
29:29
Enumerables in Objects (Cont.)
31:13
File Processing
31:15
Example
31:45
Enumerables in Objects (Cont.)
33:07
collect
33:23
select
34:11
reject
34:59
inject
35:29
Strings

28m 30s

Intro
0:00
Strings
0:08
Why do you want to get familiar with strings?
1:00
String Creation
1:16
new
1:28
empty?
1:50
length or size
2:10
Example
3:12
String Manipulation
4:40
slice
4:56
square brackets [ ]
5:02
token
5:40
[fixnum]
6:52
offset and length
8:40
chaining
12:42
String Insertion
12:56
insert
12:58
positive or negative index
13:46
String Updates
15:24
[token]
15:36
Examples
16:40
chop or chop!
17:54
chomp!
18:56
gsub
20:28
String Deletion
21:38
delete
21:38
String Reversal
22:46
reverse
22:52
String Manipulation
23:16
split(pattern=$, limit)
23:22
pattern
24:10
limit
24:15
upcase or upcase!
25:28
downcase or downcase!
26:02
swapcase
26:24
Incrementing Strings
27:26
next or next!
27:32
Check Out the Other Lessons
28:00
Ruby Data Types Part 1
28:12
Regular Expressions
28:18
Regular Expressions

33m 27s

Intro
0:00
Regular Expressions
0:10
How to create a regular expression
0:48
What goes inside
1:36
Metacharacters
3:10
Bracket expressions
3:14
Quantifiers
3:18
Anchors
3:20
Metacharacters
3:30
word and non-word characters
4:04
digit and non-digit characters
4:44
hexdigit and non-hexdigit characters
4:56
whitespace and non-whitespace characters
5:08
Examples
5:24
POSIX Bracket Expressions
7:48
Non-POSIX Bracket Expressions
9:48
Bracket Expression Examples
10:58
Quantifiers
12:34
Examples
13:30
Character Properties
17:24
Similar to POSIX bracket classes
18:22
More Character Properties
18:48
Examples
19:32
Anchors
20:08
Examples
21:14
Regular Expression Matching: Regexp Object
22:40
match
22:51
Regular Expression Matching: String Object
24:14
match
24:26
Regular Expression Modifier Characters
25:14
pat
25:38
Example
26:42
Regular Expression Modifier Objects
27:14
Example
28:38
Regexp Rdoc
30:40
Arrays

14m 35s

Intro
0:00
Arrays
0:12
Creating an Array with a Block
0:50
Alternative Ways to Create an Array
3:52
Checking the Class
5:14
Iterate through the array
5:26
Call the class method
5:28
Array Shortcuts
6:38
at(index)
6:44
delete_at(index)
7:28
first(n)
8:28
last(n)
9:28
Removing Duplicates
9:58
uniq or uniq!
10:04
Sorting the Array
10:48
sort or sort!
10:54
Getting the Index
11:35
index
11:56
rindex
12:38
Multidimensional Arrays
12:56
flatten
13:33
Check Out the Earlier Lesson
14:16
Ruby Data Types Part 2
14:26
Hashes

27m 48s

Intro
0:00
Hashes
0:12
Creating Hashes
1:18
Setting a Default Value
2:24
Accessing Hashes
4:16
Accessible by keys or by values
4:28
Keys must be unique
4:36
Creating Hashes
5:16
Comma-separated list
5:42
Hash rocket
8:28
Examples
10:16
Iterating Keys and Values
11:43
each_key
12:04
each_value
14:04
Merging Hashes
16:10
merge(other_hash)
16:20
Sorting Hashes
18:46
Replacing Hashes
20:57
replace(other_hash)
21:18
Converting Hashes to Other Classes
22:04
to_a
22:22
to_s
23:22
Example
24:34
Check Out the Earlier Lesson
27:22
Ruby Data Types Part 2
27:32
Math Operations, Part 1

28m 47s

Intro
0:00
Math Objects
0:12
Numeric
0:26
Integer
0:38
Float
1:02
Fixnum
1:14
Bignum
1:56
Rational
2:04
Math
2:24
Math Operations
2:36
Example
3:14
div(numeric)
4:54
divmod(numeric)
6:30
modulo(numeric)
7:23
quo(numeric)
8:18
remainder(numeric)
9:35
Operation Precedence 1 of 3
10:35
Operation Precedence 2 of 3
13:18
Operation Precedence 3 of 3
14:28
Abbreviated Math Operations
14:54
Move the operator in front of the equal sign
15:52
Numbers
16:36
Numeric Class
17:06
Numeric Methods
18:41
ceil
18:52
floor
19:32
round
19:50
Example with Numbers
20:20
Numeric Methods (Cont.)
22:20
truncate
22:28
num.step(limit, step)
23:02
Numeric Rdoc
25:26
Math Operations, Part 2

28m 51s

Intro
0:00
Math Operations
0:12
Math Module
0:24
Rational Numbers
0:44
Complex Numbers
0:52
Prime Numbers
0:58
Matrices
1:06
Math Module
1:12
PI and E
1:32
Math Module Methods
2:47
atan2(x,y)
2:56
cos(x)
3:14
exp(x)
3:44
Examples
4:38
log(x)
5:44
log(num, base)
6:34
log10(x)
7:04
sin(x)
7:34
sqrt(x)
7:52
tan(x)
8:06
Math Functions: Part 1 of 3
8:12
Math Functions: Part 2 of 3
9:32
Math Functions: Part 3 of 3
10:19
Math Module Rdoc
11:25
Rational Numbers
13:23
How to use
14:06
Example
15:02
Mathematical Ruby Scripts (Mathn)
16:25
Example
17:28
Complex Numbers
18:26
polar
18:56
rect
19:10
Complex Number Examples
19:18
Prime Numbers
20:14
each(ubound=nil)
20:44
prime?
21:22
Example
21:58
Matrices
23:15
build(row_size, column_size=row_size)
23:44
Example
24:44
Matrix Rdoc
24:58
Dates and Times

26m 1s

Intro
0:00
Dates and Times
0:12
Time Class
0:38
Methods of the Time Class
1:43
now
1:44
at(time)
2:10
Epoch & Unix Timestamp Conversion Tools
3:19
Components of a Time
5:07
Convert Time to an Array
5:54
to_a
6:08
Creating a New Time
6:48
Time.local
7:08
Year is required
7:22
Time.utc
8:12
What should be specified
9:30
More Methods of the Time Class
10:16
strftime(string)
11:26
RDoc
12:50
Date Library
16:46
Initializing a New Date
17:08
Parsing Dates
18:28
parse(string)
18:42
Today's Date
19:19
Date.today
19:22
Tomorrow's Date
20:22
Next
20:28
Next week
21:22
Count Down
21:26
Count Up
22:37
Components of a Date
23:20
Converting to Datetime
23:48
to_datetime
24:00
Initializing a Datetime
24:24
Converting to Time
25:23
self.to_time
25:32
Methods: Part 1

31m 24s

Intro
0:00
What is a Method?
0:12
Basic Method
0:58
Return Value
4:37
return
4:46
Factorial Example
6:18
Example
8:46
Return Two Values
10:06
Set the return keyword
10:14
Collected and returned as an array
10:28
Undefining Methods
11:22
undef method_to_undefine
11:44
Example
12:32
Method Names
13:02
Begin with lowercase letter
13:16
Separate longer words with underscores
13:26
Can end with equal sign, question mark, or exclamation point
14:03
Equal sign
14:26
Method Names with Question Mark
14:44
empty?
15:24
Method Names with Exclamation Point
16:01
mutators
16:12
! means use with caution
16:46
Method Aliases
18:05
alias new_method existing_method
18:42
Operator Methods
20:00
Operators
20:02
Array Operators
20:10
Unary Operators
20:32
Binary Operators
20:40
Example
21:28
Methods and Parentheses
25:00
Optional in most cases
25:20
Required in other cases
27:13
Methods and Blocks
27:54
Associated with blocks
28:18
block_given?
28:26
yield
28:36
Example
29:24
Methods: Part 2

20m 11s

Intro
0:00
Methods with the Unary Ampersand Operator
0:14
&
0:34
Block to a Proc
0:56
Example
2:02
Proc object
3:58
Example
5:04
Methods with Default Values
5:54
Example
7:12
Methods with variable-Length Arguments
8:05
How to create it
8:36
Example
11:06
Using Hashes with Arguments
13:02
Multiple arguments
13:08
Solution
13:30
Example
14:56
Rdoc
18:12
Classes: Part I

26m 51s

Intro
0:00
Classes
0:10
Definition of a class
0:14
Class represents a container
0:32
Can be reused
0:46
Creating our First Class
1:00
Keyword class will create new class
1:06
Name must begin with capital letter
1:30
Instantiating Our First Class
2:46
New will create a new instance of class
2:58
Initializing Values
3:58
Definition of def
4:14
Instance method
5:08
Example
7:02
Defining the to_s Method
8:24
Creating a string representation class
8:34
Example
10:54
Self in the Class
12:16
Definition of self
12:26
Example
13:54
Accessor Methods
15:52
getter methods
16:22
Example
17:00
Setter Methods
18:00
Mutator methods
18:02
Example
19:46
Automating Getter and Setter Methods
21:10
Defined in the module class
21:30
attr_reader
21:54
attr_writer
22:48
attr creates getter and setter methods
23:50
Example
24:28
Notes on Ruby's Accessor Methods
25:32
Classes: Part II

26m 42s

Intro
0:00
Defining Operators
0:10
You can define arithmetic operators
0:32
Unary Operators
0:46
Let's define operators in our class!
0:56
Example
2:52
Class Methods
6:24
Examples
6:56
Opening Up the Class
9:38
Adds an additional method
9:54
Examples
11:04
Array and Hash Access Method
15:40
Use square brackets
16:02
Define your own has access method
16:08
Example
16:56
Enumerating The Values
18:40
Define the each iterator
18:40
Testing for Equality
19:36
Class Triplex
19:50
Examples
20:54
Constants
25:00
Usually defined at the top of class
25:24
Classes: Part III

53m 36s

Intro
0:00
Class Variables
0:14
Example
2:16
Ruby Glass Jar Example
8:50
Class Instance Variables
10:20
Instance variables of class objects
10:46
Advantage of class instance variables
11:18
Examples
11:30
Method Visibility
16:16
Three types of method visibility
16:26
Public methods
17:34
Private methods
17:38
Protected methods
18:04
Invoking Method Visibility
19:21
Public , Protected, and Private Visibility
19:22
Invoking Method Visibility With Arguments
21:39
Example: Invoking Method Visibility
22:12
Class Visibility
23:31
Instance and Class Variables are Private
23:32
Constants are Public
24:00
Makes Existing Class Methods Private
24:27
Makes Existing Class Methods Public
25:08
Example: Class Visibility and class GlassJar
25:43
Subclassing
27:08
Subclassing: Subclass and Superclass
27:09
Example: Subclassing
29:43
Inheritance
30:05
Inheritance
30:06
Example: Inheritance
31:25
Subclassing and Inheritance
31:34
Descendants
31:41
Ancestors
31:56
More On Descendants and Ancestors
32:08
Extending a Class
33:27
Extending a Class
33:28
Coding Example: Extending a Class
34:24
Overriding a Method
36:41
Overriding a Method
36:42
Coding Example: Overriding a Method
37:18
Modifying Methods with Chaining
38:52
Modifying Methods with Chaining
38:53
Super
39:25
Coding Example: Modifying Methods with Chaining
39:51
The Singleton Pattern
44:52
Introduction to The Singleton Pattern
44:53
Setting Up Singleton
45:28
The Instance Method
45:58
Rdoc for Singleton: Usage
46:23
Rdoc for Singleton: Implementation
47:45
Coding Example: Singleton
49:38
Modules

24m 19s

Intro
0:00
Modules
0:04
What is Modules?
0:05
Modules Examples
0:40
Modules: Mix-Ins
3:31
What is a Mix-in?
3:32
Modules: Namespace
4:07
What is a Namespace?
4:08
Why Use a Namespace?
5:13
Example of a Namespace Module
5:59
Example of Mixing in The Module Into the Global Scope
6:00
Modules: Creation
7:04
How to Create a New Module?
7:05
Modules: Usage
8:19
How to Use It?
8:20
class Poker & class Bridge
9:13
Creating Our Module as a Mix-In
9:41
Example of a Module Using Instance Methods
9:42
Coding Example
10:20
Creating Our Module as a Namespace
12:11
Implement Class Methods for the Module
12:12
Coding Example
14:56
Loading Our Module
19:46
Loading Our Module Overview
19:47
Require & Load
20:15
Coding Example: Loading Module
20:48
Lesson Summary
23:36
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Methods: Part 2

  • If a block object is passed in a method with the unary ampersand operator '&', it will be treated as a Proc object
  • If a Proc object is passed in a method with the unary ampersand operator '&', it will be treated as a block object
  • Methods can have parameters with default values
  • To create it, the parameter name is followed with an equal sign and value
  • Methods can have variable-length arguments
  • To create it, add a * before the method's parameter
  • In the method, the parameter will refer to an array
  • Passing a hash as a parameter is more organized than passing multiple arguments

Methods: Part 2

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Methods with the Unary Ampersand Operator 0:14
    • &
    • Block to a Proc
    • Example
    • Proc object
    • Example
  • Methods with Default Values 5:54
    • Example
  • Methods with variable-Length Arguments 8:05
    • How to create it
    • Example
  • Using Hashes with Arguments 13:02
    • Multiple arguments
    • Solution
    • Example
    • Rdoc

Transcription: Methods: Part 2

Welcome back to Educator.com.0000

Today's lesson is on methods; this is the second part.0001

What I want to do for this second lesson is to go over a lot of common parameters that you will be using as part of the methods, and to give us a lot of hands-on, so you can see it in action.0011

For this one, we first want to go over the unary ampersand operator.0027

This is just this little & sign here, and it allows a block object to be treated as a Proc object.0035

So, when you have a parameter, and right before that parameter you put the & sign, it's going to treat whatever block object as a Proc object.0045

I like to call this block to proc.0056

In the previous lesson, you saw that we used this processor method; this processor method took one argument, and it passed a block.0062

This time, we're actually using that processor, but notice, it has two arguments: one is arg, and the next one is actually this unary & operator.0074

This is what is going to change that block to a Proc.0087

For this example, we call Process, and it calls this method call in it.0092

That method 'call' is going to take that block, and call it...plus pass this argument--this arg.0104

Let's do an example and see it in action.0115

Let me clear that terminal out; first, let me find it.0119

I'm going to take the exact same one from the slide, and then Process.call(arg)...0124

I have my method; it's done; and then, for this one, I'm just going to call the processor, pass in the value 10, and then I'm going to pass that block, x times 2.0132

Even in this example, my second parameter--I never actually pass it in; I put a block at the end.0152

It understands that that block is part of the parameter, and it's going to convert that to a Proc, so I can call it now.0165

At the same time, I can go ahead and change the block value, which is going to change the return result--change our parameter, and that is going to change the result, too.0179

Also, if I just do 10, notice I get a NoMethodError, because it's trying to call the method call, but it has no Proc object to call it in.0191

I could easily fix that by just putting an empty block, and it's going to have to return nil.0202

That is where I pass in my value, and you notice that whatever value I put in there, it's going to return that value back, but I'm not actually doing any processing for this example.0210

OK, so, at the same time, this unary & operator can go the other way, so you can treat a Proc object to be a block.0227

A Proc object can be treated as an ordinary block...so this is a Proc to a Block.0243

For this example, I create this Proc object using Proc.new, and this says, "Whatever this value is, I want you to square it; make that value x times x," so I call it square.0253

I'm going to use this with the Array object, using the map method.0272

I have this Array; it calls map; I pass in my Proc object with that unary & operator, and it takes these values and squares them, so I end up with 1, 4, and 9.0279

Let's go ahead and do an example; I can just do square.Proc.new(x^x), and then I can pass in an Array, take the map, and then pass in my value with that.0301

And it squares the values up.0325

The greatest thing is this dynamic: I can pass as many values as I want, and it will process all of them.0328

This is an example of our object--Proc to a block.0339

Next, we want to go over default values; I actually showed you that in the first lesson, with the basic method.0350

This default value creates a parameter, and you follow it with an equals sign and a value: that is how you create it.0360

That will create your default value.0370

If I don't pass any parameter in there, it's going to use that default value.0373

This allows a method that can take an optional number of arguments.0378

All these ones with default values--I don't need to specify what it is; it will just use a default value.0383

The example: I have this adder method; it takes two parameters, but notice, that second one has my default value.0391

It has a default value of one.0403

If I just did adder, and I just passed 2, it would return to me the value 3, because b=1 is the default value.0411

Let's go ahead and show you this in some code.0427

I'm just going to pass that same one in; it takes two parameters and adds the values up.0432

I just pass 1; it's going to do 1+1; but also, if I do adder(1,5), it's not going to use that default value.0443

Since I passed in 5 for b, it says, "OK, this has prior precedence," so it's going to do 1+5.0455

I can also just do 2--it would be 3; adder(2,2) does 4; (10,20)--it's going to add them up and be 30.0464

That is our default value.0478

Next, let's look at methods with variable-length arguments.0486

This is a very interesting parameter that allows us to put a lot of arguments in the method without specifying all of them and saying what they need to do.0494

This allows parameters that allow an arbitrary number of arguments.0508

How do I create it? You add this star before the method's parameter.0516

The arguments will be passed as an Array into the code.0524

All these arguments that you pass--when it sees that star, it's going to get that variable, and it's going to be returned as an Array.0533

Make sure to process it as an Array in that case.0541

What I do here is, I have this method can min_value; my parameter is that variable-length argument.0545

This is a variable-length argument...and it's called Numbers; it takes a length of numbers.0560

This method gets the lowest value, and it returns that.0578

Let's go ahead and just go through the code really quickly.0584

The first one does a Numbers.shift, so--this Numbers is an Array; it's going to take the first element in this Array and say, "This is the minimum value."0589

Then, it's going to go through each of the other values here, index 1+...to the end; if it finds a value that is lower than the minimum, then it's going to make that the minimum value.0601

It's going to continue on this loop until it goes through all of them, and then, now, we have found the minimum value.0620

This iterates through the Array and gets the minimum value.0628

Now, it goes through all this; min actually points to the minimum; and then, it returns that value here.0656

I want to show you this in action, so let's go ahead and do min_value; it takes a parameter of Numbers; go ahead and do that Numbers--it gets the first element in that Array.0667

Then, we're going to iterate through that Array of numbers, getting the lowest one.0685

To do that, I'm going to get min=n if whatever element that is less than what is the minimum.0693

Then, at the end, I want to return min; so that is my least value there.0701

This takes a variable length of arguments, and I don't have to worry about it as I pass; I just put a comma list in.0706

I'm going to call min_value, and I can call [1,2,3,4,5,6,7], and when I press Return--you know what that code is doing--it says 1 is the lowest.0716

I can also go through a different list, where the last value is maybe a negative sign, then put some other values in there, press Return...it says the minimum value is -5, so I know it's getting the last value and going through all of them.0730

And, it works with negative numbers, too.0751

I can also use parentheses, remember...it still works; it gets the minimum values from that.0758

That is our variable-length arguments.0771

The next one is...you will commonly say, "While I'm programming, I have so many parameters I'm passing--it's going to get disorganized; it's going to get confusing; I don't want to pass it in a certain order--I want more flexibility when I code."0778

That is the reason we should use Hashes--multiple arguments that get disorganized, that get difficult to remember in the proper order.0795

I just want to work the code and get it processed.0807

Solution: pass a Hash as a parameter.0809

Depending on what you're doing, you will want to have this flexibility.0815

You might want to force it to have a certain amount of order in the primers, but in this case, we're being flexible; we're just saying that we're going to use that Hash; we're going to process it as a Hash.0821

Here in my example, I have this method called multiplier; it takes Args, which is a Hash.0833

In my code, I actually didn't default it to a Hash, but I can make a default value a Hash here, too.0848

It's going to take four keys in the Hash and multiply them together; that is why it's called multiplier; it multiplies four elements.0857

Look at my code; notice, it actually looks for a symbol called key 1.0868

If that key doesn't exist in the Hash, it's going to default it to value 1.0874

The same for key 2; if it doesn't exist, it's going to default it to value 2; the same as 3 and 4.0879

At the end result, it's going to multiply them together and return that value.0888

Let's make this example in our code.0895

Let's go ahead and add the parentheses this time, since we haven't been using that.0901

I'm going to go ahead and put in all the key values; notice that these are not String keys; these are Symbols.0910

I'll make it easier, just substituting the number...so, I have all my values here, and then I just want to say, "Just multiply them all together."0924

It's going to get those four values, multiply them together, and return it.0943

Now, when I call multiplier, I just have an empty Hash; it says wrong number of arguments (0 for 1); let's see, if I put those parentheses, if that fixes it...it does!0949

With a Hash, make sure you have parentheses.0963

Notice, I pass an empty Hash in there; all that is going to do is say, "You passed in a Hash; you didn't give me the indication to define them in there; I'm just going to use the default I've already defined in the code: 1 times 2 times 3 times 4, and that's going to be 24."0968

I can also define a couple of those values; so that key, 1, I make that 2, and that key 2--I'm going to make that 3.0986

This is going to be 2 times 3 times 3 times 4, and I get 72.1003

I actually can define them all; I'm going to define them all as 1, so my value should be 1, too.1010

My value is 1: 1 times 1 times 1 times 1.1025

Notice, I'm passing a bunch of different values--some of them I don't even define, but it's allowing me to do it, because I'm using this Hash, and in my code, I tell it these default values that I can specify.1029

For this one, it's 5 times 2 times 3 times 4; it's 120.1051

Remember, I can still pass in other parameters to this.1062

I have this Hash, but I can also pass in other parameters after this, and I can still process it, also.1065

Depending on what you're doing...I just want you to get the concept down.1072

That is using Hashes with arguments.1080

Let's quickly go over the RDoc for the method.1083

It's very simple; it has method, and it has Proc, because they are so closely integrated.1093

Proc to block, block to Proc...we talked about that...1103

Notice here, it does have some methods to check for equality: "Two method objects are equal if they are bound to the same object and refer to the same method definition."1107

You already saw the call method in action--"Invokes the meth with specified arguments, returning the method's return value."1116

There is a method called arity--"Returns an indication of the number of arguments accepted by a method."1128

You already saw the call method...1135

You can also use inspect or to_s to return "the name of the underlying method."1140

This is interesting; you can also call parameters, and it "returns the parameter information" of that method.1148

Receiver "returns the bound receiver of the method object."1156

We already talked in a previous lesson about unbind--"Dissociates meth from its current receiver."1160

Let's see that in action--this parameters.1169

So, multiplier.parameters...wrong number of arguments...it's probably not being used in the right way...1176

Anyway, I will let you look deeper into that RDoc.1196

That is the end of the methods lesson, part 2 of 2.1202

See you again at Educator.com!1208

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