Notes on Ruby

I thought I’d write some note on my month of Ruby. Mainly to cement my learning. I find writing things down helps my process. I’ll keep adding to post as and when I want to make a note of something I find interesting.

Comments:

# single line of comments (I'll use this to
show console output)

=begin
lots of
lines of 
comments
between these
markers
=end

Variables:

You set a variable by giving it a name eg. country, first_name, last_name. Convention is to keep them lowercase with underscore between words.

first_name = "John"
last_name = "Smith"
age = 65
adult = true

How to capitalise:

first_name = "john"
first_name.capitilize # John

How to uppercase or lowercase:

first_name.upcase   # JOHN
first_name.downcase # John

Reverse & length:

first_name.reverse # nhoj
first_name.length  # 4

Printing to the console:

print first_name.upcase # JOHN

print and puts do two different things, prints adds everything in line in the console. Puts shows things on each line.

print first_name.upcase
print last_name.upcase

# JOHNSMITH

puts first_name.upcase
puts last_name.upcase

# JOHN
# SMITH

How to add a variable in to a string:

puts "My name is #{first_name}."

# My name is John.

Maths:

All the classic maths operators.

Addition (+)
Subtraction (-)
Multiplication (*)
Division (/)
Exponentiation (**)
Modulo ({151bccf5f64c347946bc19dad4e6e94d96340062ed0c390499aa4e37c867c926})

var = 4 + 4
print var    # 8

var = 5 - 1
print var    # 4

var = 3 * 3
print var    # 9

var = 6/2
print var    # 3

var = 2**3
print var    # 8 ( 2*2*2 )

var = 9 {151bccf5f64c347946bc19dad4e6e94d96340062ed0c390499aa4e37c867c926} 2
print var    # 1 ( 2 goes in to 9 four times with 1 remainder )

Comparisons:

and: – && – both have to be true
or: – || – only one has to be true
reverse result: – ! – opposite

( 8 == 8 ) && ( 2 == 2 )  # true
( 3 == 1 ) || ( 4 == 4 )  # true
!( true )                 # false

Control flow

If this is true

else if this true

else

end

In the next the code I will write a code to replace the letter “h” with “aitch” in a given string using global substitution. A bit pointless but fun all the same. Often you have to sanitise text coming in to a database to make sure no odd data is entering your system so knowing how to manipulate text is useful.

You can have many else if statements but there is a better way to do this with a case statement.

if first_name.include? "h"
  first_name.gsub!(/h/ "aitch")
  puts "Hello, #{first_name}!"
else
  print "No 'h' in this string"
end