Coding style
snake_caseSubstrings
# executed in 'irb':
>> greeting = "Hello Everyone!"
=> "Hello Everyone!"
>> greeting[0..4]
=> "Hello"
>> greeting[0..14]
=> "Hello Everyone!"
# negative positions count back from the end
>> greeting[6..-1]
=> "Everyone!"
>> greeting[6..-2]
=> "Everyone"
# .length
>> greeting.length
=> 15
# .split
>> greeting.split
=> ["Hello", "Everyone!"]
# .split with an argument
>> numbers = "one,two,three"
=> "one,two,three"
>> numbers.split
=> ["one,two,three"]
>> numbers.split(",")
=> ["one", "two", "three"]
# .sub - substitute - replaces just a single occurence
>> numbers
=> "one,two,three"
>> numbers.sub(',', '-')
=> "one-two,three"
# .gsub - global substitution - replaces all occurances
>> numbers.gsub(',', '-')
=> "one-two-three"
# string concatenation
######################
name = "meleu"
puts "Hello, " + name + "!"
# Hello, meleu!
# string interpolation
######################
puts "Hello, #{name}!"
# Hello, meleu!
# executing code inside interpolation
#####################################
modifier = "very "
mood = "excited"
puts "I am #{modifier * 3 + mood} for today's class!"
# I am very very very excited for today's class!
Symbols are halfway between a string and a number.
They start wit a colon then one or more letters, like :flag or :best_friend.
Think of a symbol as a "named integer". It doesn't matter what actual value the symbol references. All we care about is that any reference to that value within the VM will give back the same value.
[I need to see some examples of how can this be useful]
Two basic kinds of numbers:
Numbers are objects and have methods (try 5.methos inside irb to see the list).
Example of a loop:
5.times do
puts "Hello, World!"
end
Block styles
# do/end style
5.times do
puts "Hello, World!"
end
# bracket style
5.times{ puts "Hello, World!" }
Blocks are passed to methods. In the examples above 👆 we're giving to the method 5.times the instructions we want to run each time.
There are many methods that accept blocks, like gsub:
>> "augusto 'meleu' lopes".gsub("u"){ puts "Found an U!" }
Found an U!
Found an U!
Found an U!
=> "agsto 'mele' lopes"
When our instructions within a block need to reference the value that they're currently working with, we can specify a block parameter inside | pipe characters:
5.times do |i|
puts "#{i}: Hello, World!"
end
>> numbers = [1, 2, 3, 4]
=> [1, 2, 3, 4]
# the "shovel operator" << works like .push
>> numbers << 5
=> [1, 2, 3, 4, 5]
>> numbers
=> [1, 2, 3, 4, 5]
# there conveniente methods, like .first, .last, .min, .max, .minmax
>> array.last
=> 5
>> array.first
=> 1
>> array.max
=> 5
>> array.min
=> 1
>> array.minmax
=> [1, 5]
# .sort
>> numbers = [1, 9, 2, 8, 3, 7]
=> [1, 9, 2, 8, 3, 7]
>> numbers.sort
=> [1, 2, 3, 7, 8, 9]
>> numbers
=> [1, 9, 2, 8, 3, 7]
Others methods to try:
eachcollectshuffleSee full Array documentation: https://ruby-doc.org/core-2.5.1/Array.html (2.5.1 because that's the version used in The Well-Grounded Rubyist)
Hashes are basically an associative array. In other words: a hash is an unordered collection where the data is organized into key/value pairs.
produce = {'apples' => 1, 'oranges' => 2}
# => {"apples"=>1, "oranges"=>2}
puts "there are #{produce['oranges']} oranges in the fridge."
# there are 2 oranges in the fridge.
# => nil
# it's also possible to use symbols as the keys of a hash
produce = {apples: 3, oranges: 4}
=> {:apples=>3, :oranges=>4}
# now you must use the :symbol notation to get the value
puts "there are #{produce[:oranges]} oranges in the fridge."
# there are 4 oranges in the fridge.
# => nil
Common conditional operators: ==, !=, >, >=, <, <=.
Logical AND: &&
Logical OR: ||
The convention is that a method which returns a boolean value should have a name ending with ?.
Example:
class Student
attr_accessor :first_name, :last_name, :primary_phone_number
def introduction
puts "Hi, I'm #{first_name}!"
end
end
frank = Student.new
frank.first_name = "Frank"
frank.introduction