Learning Ruby

Let's Learn Ruby AQAP

As Quickly As Possible!

Run the interactive ruby shell – irb

Suggest using Netbeans – download ALL

Running Ruby Code

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2 + 6

22 / 4 5Float(22)/4

22.0 / 4

3 * 3

3 ** 3

big_number = 1_000_000_000 (underscores not required and can go anywhere allowed to make it more readable – commas hard to see)

Simple Ruby Number Objects

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Math.sqrt( 9 )

Math.methods

9.methods will tell you what methods can be used with 9

27.class will tell you what class 27 belongs to (Fixnum)

3.times { print "Ho! " }

1.upto( 5 ) { |i| puts i } defines i as the iterator variable

termed a “code block” Anonymous delegate given the name i

Ruby Number Methods

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one = "1"two = "2"

one + two string concat, right?Integer( one ) + Integer( two ) casts and then adds

12.to_s calls to string method, but wants you to request conversion

print "Happy ", 12.to_s, "th Birthday!"puts "Happy ", 12.to_s, "th Birthday!"puts "Happy " + 12 + "th Birthday!"

Number Conversions

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a1 = "this is a string\n” evaluate backslash and contents of #{} inside of the string. Termed string interpolation

a2 = 'and so is this\n‘ will see the \n as no evaluation is done

print a1print a2

answer = “joy”

puts "The meaning of life is #{answer}"

puts "There's #{24*60*60} seconds in a day"

Ruby String Objects

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formatted_text = <<END_OF_TEXTLet us turn our thoughts today

To Martin Luther KingAnd recognize that there are ties between us

All men and womenLiving on the Earth

Ties of hope and loveSister and brotherhood

That we are bound togetherIn our desire to see the world become

A place in which our childrenCan grow free and strong

END_OF_TEXT any delimiter – as long as it matches

print formatted_text interpretation does work

Ruby Here Documents

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String.methods.sort sorted list of String methodsformatted_text.size number of characters

formatted_text.downcase lowercaseformatted_text.upcase uppercase

formatted_text.capitalize! ! means to actually change the object in place (rather than return a changed copy)

formatted_text.reverse reverses all characters

formatted_text.empty? boolean indicated by ? only used in method names (not variables)

Ruby String Methods

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song_lines = formatted_text.to_a to array(1..10).to_a [1,2,3,4,5,6,7,8,9,10] from a range (denoted ..)(‘a’..’e’).to_a [“a”, “b”, “c”, “d”, “e”]

print song_lines[1]print song_lines[5]print song_lines[99] Gives nil if used when out of

range, will add to array if assign outside of range.

print song_linesprint formatted_text

song_lines.class Arrayformatted_text.class String

Working with Ruby Strings

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Same variable can hold any type at different times…a = 42puts aa = "The Ruby Programming Language"puts aa = 1.8puts a

What About Variable Type?

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Everything - numbers, strings, data structures, Class itself etc. - is an object

Methods are invoked using the dot (".") notation

Variables are dynamically created as needed (problems with typos), but will tell you during execution if you access something without a value.

The traditional notion of a variable's "type" is not something the Ruby programmer concerns themselves with (too much)

Ruby So Far

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