Getting Help
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ruby-lang.org Primary resource for Ruby "Ruby Website"
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ruby-doc.org Official documentation for Ruby.
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Running Single Commands
ruby -e 'puts 123' |
ruby -e 'print 123' |
ruby -e 'puts "Hello".reverse' |
Accessing IRB
irb |
irb --simple-prompt |
Comparison/Logic Operators
Equals |
== |
Less than |
< |
Greater than |
> |
Less than, equal to |
<= |
Greater than, equal to |
>= |
Not |
! |
Not Equal |
!= |
And |
&& |
Or |
|| |
Conditionals: if, else, elsif
x = 1
if x == 1
puts "Text here"
end
if x == 2
puts "Text here"
else
puts "Text here"
end
if x == 2
puts "Text here"
elsif x == 1
puts "Text here"
else
puts "Text here"
end |
Conditionals: unless, case
x = 1
unless x == 2
puts "This runs if the above boolean is false."
end
case
when boolean
puts "Text here"
when boolean
puts "Text here"
else
puts "Text here"
end
case test_value
when value
puts "Text here"
when value
puts "Text here"
else
puts "Text here"
end |
Inline Conditional
puts "test" if name == "Frank" |
Ternary Operator
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x = boolean ? "test 1" : "test 2" This will assign one of the 2 values based on the boolean result.
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OR/OR-EQUALS Operator
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x = y || z If y has a value set x equal to y else set it equal to z.
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x ||= y If x has a value, nothing happens. If it does not then set x to the value of y.
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Loops
x = 0
loop do
x+=2
break if x >= 20
puts x
end |
You can use the following within a loop
break Terminate the whole loop
next Jump to the next loop
redo Redo this loop
retry Start the whole loop over again
Loops: while
x = 0
while x < 20
x += 2
puts x
end
# You can also use the inline version
x = 0
puts x += 2 while x < 100 |
Loops: until
y = 23245
until y <= 1
puts y /=2
end
# You can also use the inline version
y = 23245
puts y /= 2 until y <= 1 |
Loops: for
fruits = ['banana', 'apple', 'pear']
for fruits in fruits
puts fruit.captialize
end |
Iterators
5.times { puts "Hello" } |
1.upto(5) { puts "Hello" } |
5.downto(1) { puts "Hello" } |
(1..5).each { puts "Hello" } |
array.each { |num| puts num * 20 } |
You can use do and end inplace of { }
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Variable Scopes
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Global Variable $variable = "Test"
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Class Variable @@variable = "Test"
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Instance Variable @variable = "Test"
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Local Variable variable = "Test"
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Block Variable variable = "Test"
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Integers
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1234.class This will tell you what class the Integer object belongs to.
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10.2.to_i Will convert number to integer.
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Stored in 2 ways: Fixnum and Bignum
Floats
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12345.10.round Rounds the float to integer.
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12345.to_f Converts a integer to a float.
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12345.10.floor Rounds down to whole number.
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12345.10.ceil Rounds up to whole number.
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String Methods
"Hello".reverse |
"Hello".capitalize |
"Hello".downcase |
"Hello".upcase |
"Hello".length |
"Hello".upcase.reverse |
Strings can be in single or double quotes. Ruby will always return them in double quotes.
Constants
Similar to variables, not true objects.
A constant should not change unlike a variable.
Define constants in all CAPS
TEST = 2
Anything that begins with a capital letter at the beginning is considered a constant.
If you try to change the value of a constant, it will display a warning, but will still change the value. |
Boolean Methods
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z.nil? Will check if the variable z is == to nil
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2.between?(1,4) Will check if the number 2 is between 1 and 4
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[1,2,3].empty? Will return true/false if its empty.
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[1,2,3].include?(2) Returns true/false if the number 2 exists in array.
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{‘a’ => 1, ‘b’ => 2}.has_key?(‘a’) Returns true/false if the key exits.
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{‘a’ => 1, ‘b’ => 2}.has_value?(2) Will return true/false if the value exits.
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Arrays
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data_set = [] Sets an empty array, and also clears out existing array
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data_set = [“a”, “b”, “c”] Sets an array with data
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data_set[1] Returns data from the defined positioned.
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data_set[0] = “d” Sets the value of the element with key 0 to d
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data_set << “e” Appends the data to the array
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data_set[1] = nil Removes data from an array
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data_set.clear Clears out an array
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Array Methods
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array.inspect Will return a string representation of the array.
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array.to_s Joins array elements together.
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array.join(",") Will implode the array by comma.
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x = “1,2,3,4,5”; y = x.split(‘,’) This will return an array, separating each value by comma.
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array.sort Will sort your array asc order
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array.uniq Will return an array with no duplicates
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array.uniq! Will update the array with the new version in place.
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array.delete_at(2) Will delete the element based on key and return the value that it it deleted.
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array.delete(4) Will delete the element based on value
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array.push(4) Will add to an array - last position
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array.pop Will remove the last element from the array
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array.shift Will remove the first element from the array
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array.unshift(1) Will put the value to the front of the array
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array + [9,10,11,12] Will take first array and add these other values from the second array to it.
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array - [9,10] Willl search and remove the values 9,10
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Hashes
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mixed = {1 => [‘a’, ‘b’, ‘c’], ‘hello’ => ‘world’, [10,20] => ‘top’} You can have mixed values in hashes.
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mixed.keys Returns all of the keys
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mixed.values Returns all of the values
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mixed.length Returns the length of the hash
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mixed.size Returns the length of the hash
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mixed.to_a Converts the hash to an array
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mixed.clear Will return an empty hash
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mixed = {} Will return an empty hash
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mixed.key('world') Will return the key of the hash value.
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mixed['test'] = 'value' Will add/set value to hash.
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mixed[[10,20]] Returns the value for the hash key which is [10,20]
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Symbols
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:test Prefixed with a colon and stored in memory once where as a string is stored in memory each time.
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hash = {:first_name => “Frank”, :last_name => “Perez”} Works well with hashes.
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hash[:first_name] You will need to reference the symbol from the hash like such.
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A label used to identify a piece of data.
Ranges
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1..10 Inclusive Range
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1...10 Exclusive Range
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(1..10).to_a Converts the range to an array.
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(1..10).class Will let you know that its a range.
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x = 1..10 Sets a range to the variable x.
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x.begin Returns the first number.
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x.first Returns the first number.
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x.end Returns the last number.
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x.last Returns the last number.
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z = [*x] Using the splat operator *, you can assign the range as an array.
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y = 1...10; y.include?(10) Returns false, as it is not included in the range.
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alpha = ‘a’..’m’ Creates an inclusive range of letters.
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alpha.include?(‘g’) Will return true, as it exists in the range.
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[*alpha] Will return all the letters in the range, array format, shorthand.
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Inclusive ranges include all numbers in a range where exclusive ranges excludes the last number.
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