Ruby Programmint Recommendation and Tips

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Ruby

pry

Tips:
help, ls command

  1. Duck typing
  2. Object Model
  3. metaprogramming
  4. tainting
  5. package gem
  6. document ruby code

Part one- Facets of Ruby:

Chapter 1- Getting Started

Rdoc and ri for Ruby documentation, pry also have the doc,

Chapter 2- Ruby.new

Every object has a unique object identifier.
Methods are invoked by sending a message to an object.

Class Variable: @@total
Global Variable: $debug
Constant Name: PI

Array initialization: a = %w{ test tao zhang xiao}
Hash initialization: h = Hash.new(0) for like counting the words

Regex: \s \d \w, =~, is match.

Block and Iterators: use yield() 反调block中的变量。

Command-Line Arguments: ARGV array, print gets, p

Chapter 3- Classes, Objects and Variables

initialize is the constructor in Ruby.
attr-reader, attr-accessor method to provide set and get method.
CSV reader. String.dup to duplicate the string object and String.freeze the object, the object can’t be changed.

Chapter 4- Containers, Blocks, and Iterators

Arrays, can be accessed by the negative index which is calculated from the end.
a[1..3], a[1…3] no include the last one, a[-3..-1]
shift, pop and push is supported by Array by the default. push+shift=Queue, push+pop=Stack

Hash can be indexed by Regex, Symbol and String. Ruby remember insert order of hash when try to iterate it.
String.downcase, String.scan search the string to regex. Hash.sort-by {block}

Ruby iterator is a method that can invoke a block of code.
swap: a,b=b,a, Container.each-with-index, Array.inject(:+) calculate the sum of the array. loop is while(true).

block-given? test give block or not.

ruby
lambda { p “test” }

lambda will create a Proc.new for the block.

Chapter 5- Sharing Functionality: Inheritance, Modules, and Mixins

Inheritance <, mixins include keyword

Chapter 6- Standard Types

3.times, 1.upto(5), 10.downto(1), 50.step(10,2) iterator generate way.

Chapter 7- Regular Expression

Chapter 8- More about Method

Chapter 9- Expressions

defined? check method
Comparing objects: ==, ===, <=>(General comparison operator), =~, eql?(same type and equal values) and equal? (same object ID

Chapter 10- Exceptions, catch and throw

Tiding up, begin-rescue-end.

Chapter 11- Basic Input and Output

IO Object, File, STDOUT, endl, StringIO, open()

Chapter 12- Fibers, Threads, and Processes

Fiber: Fibers let u suspend execution of one part of program and run some other part. Run the code later.
Multiple thread, multiple process: split up cooperating tasks.

Fiber, Fiber.new, Fiber.yield, Fiber is used for abstractions, like enumerate.
Fiber can transfer the control, continuation is a way of recording the state of the running program, like web app request.

Multiple thread, green thread by Ruby. Multiple Processes, system(“linux system command”).

Chapter 13- Unit Testing

Test::Unit::TestCase, assert-equal(), assert-match, assert-empty, assert-same

Chapter 14- When Trouble Strikes

Use nonbuffered I/O(set sync=true) for debug messages.

ruby
num1, num2 = line.split(/,/).map { |val| Integer(val) }

has.rehash to rehash the elements in hash, like object hash value.
benchmark to test the performance.

Part two- Ruby in Its Setting

Chapter 15- Ruby and Its World

gem query –details –remote –name-matches builder
gem list –all, list all versions
gem environment gemdir
gem server, open a gem document server for listing the installed gems.

rake developed by Jim Weirich, was initially implemented as a Ruby version of Make. But rake is an automation tool, run tasks.
Thor is a tool that makes it easy to write Ruby command-line tools.

Chapter 16- Namespace, Source Files, and Distribution

Math::E, Math::PI, namespace.

Chapter 17- Character Encoding

Not too much to talk about that.

Chapter 18- Interactive Ruby Shell

conf, configuration fo the IRB,

Chapter 19- Documenting Ruby

Explain how to use Rdoc and ri to document the ruby

Chapter 20- Ruby and the Web

Talk about the CGI: common gateway interface, cookies and sessions, which includes all the lower-level details.

Chapter 21- Ruby and Microsoft Windows

Discuss with about the Win32API, win32ole module. to interact with windows, Windows shell.

Part Three- Ruby Crystallized

=begin =end is ignored by Ruby and used to comment and docs.

Type Meaning
%q Single-quoted string
%Q, % Double-quoted string
%w, %W Array of strings
%r Regular expression pattern
%s a symbol
%x shell command

usually %r for regex %w for string array, %x for command, %q for string for multiple lines.

Chapter 22- Ruby Language

Basic Types

numbers, strings, arrays, hashes, ranges, symbols, regex
Fixnum to Bignum automatically,
String is different in dilimited and substitution.
?\C-a #=> “\x01”
?\C-d $=> “\u0004”

Ranges: expr..expr like 1..3, expr…expr will exclude the last element.

Array: %w only set the words array no substitution, %W will make substitution of individual word.

Symbol: In some lang is called atoms and the process is called interning. :”#{a}ello”

Regex: /pattern/options, %r{pattern}options
options can be:
| Options | Meaning |
| — | — |
| i | case insensitive |
| o | substitute once |
| m | match new line |
| x | allow spaces and comments |

Variables :
P.320 Pattern Matching Variables, Input/Output Variables, Exexution Environment Variables,

break, redo and next.

{}, Proc, lambda {}

Chapter 23- Duck Typing

An object’s type is determined by what it can do, not by its class!!

names.map { |name| name.upcase} is equal: names.map(&:upcase), &:upcase will be changed into to_proc of upcase.

Chapter 24- Metaprogramming

Metaprogramming, provide the ability to design a new, domain-specific programming language to solve particular problem.
P366, A Ruby object has three components:

  1. A set of flags
  2. some instance variables
  3. an associated class
    self refers to the read-only current object
    puts 这种方法的调用过程，从self开始，把self作为method receiver，如果没有方法就继续找他的supperclass，直到最后的BasicObject，如果没有就报错。P.367有详细说明了这个过程。

P.369, 里面讲了怎么给已经有class的ruby object加入他们的method，ruby会让他们继承自一个anonymous class，singleton class，来实现这个方法。

ruby
animal = ‘cat’  
def animal.speak
    puts “The #{self} speaks words”
end

In ruby the instance variable is created withe the class, not the instance of the class. So use self.val to access to the variables.

ruby
singleton = class << animal
    def lie
        puts “The #{self} is lying.”
    end
    self
end
puts singleton.instance_methods - ‘animal’.methods

在ruby中子类修改父类的私有函数，只需要用public :method_name，ruby会建立个新的同名method然后super调用，返回结果。
P.376 Ruby中的Modules和Mixins的实现方式就是，用anonymous class的方式来将方法指向module同时super class保持正常，既提供了功能同时，也可以合理的建立super class chain。
P.378 24.5 Metaprogramming Class-Level Macros，这一块很爽，讲了关于attr_accessor还有has_many的实现技术。

通过这个方式来创建了add_logging，同时用log方法就可以调用。

ruby
class Logger
    def self.add_logging(id_string)
        define_method(:log) do |msg|
            now = Time.now.strftime(“%H:%M:%S”)
            STDERR.puts “#{now}-#{id_string}: #{self} (#{msg})”
        end
    end
end

Ruby Struct.new(:name, :address, :likes) 可以新建的class只带有attributes，并且可以被< extend 继承。
P.384 Class.new的神奇用法,instance_eval 将设置self，直接调用caller的method。9,10小节没有怎么看明白.

Chapter 26- locking Ruby in Safe

Ruby中的safe模式，$SAFE里面存着现在的safe等级从0到4，可以用Object#taint，tainted？，trust来判断object的可信度。

Rails 里面有些ruby没有的内置方法，包括Stirng.to_time, 直接把string转换成时间格式。