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Content
• CONDITION
• ARRAYS
• HASHES
• BLOCKS

CONDITION
• If statement
• If modifier
• Multiple if
• If else
• If else modifier
• Unless if
• Unless if modifier
• Case statement

Ruby if… Statement
SYNTAX
if conditional [then]
code...
end
• Note: The end keyword is required to indicate the
end of the if.

Example 1
To check some value greater or not
a = 42
if a > 7
puts "Yes“
end
Output:
yes

Example 2
To check two conditions
num = 16
if num > 7
puts "Greater than 7“
if num < 42
puts "Between 7 and
42“
end
end
Output:
Greater than 7
Between 7 and 42

Ruby if else… Statement
SYNTAX
if conditional [then]
code...
[elsif conditional [then]
code...]...
[else
code...]
end
• Note: The end keyword is only needed for the if statement, as
the else block is part of the if expression.

Example 3
To guess the age
age = 15
if age > 18
puts "Welcome“
else
puts "Too young“
end
Output:
Too young

Example 4
To guess the number greater than 2 or not
x = 1
if x > 2
puts "x is greater than 2"
elsif x < 2 and x!=0
puts "x is 1"
else
puts "I can't guess the
number"
end
Output:
x is 1

Example 5
To guess the number
num = 8
if num == 3
puts "Number is 3“
elsif num == 10
elsif num == 7
else
puts "Not found“
end
Output:
Not found

Ruby if modifier
SYNTAX
code if condition
• Note: Executes code if the conditional is true.

Example 6
To guess the number
debug = 1
print "debugn“ if debug
Output:
debug

Ruby unless Statement
SYNTAX
unless conditional [then]
code
[else
code ]
end
• Note: The unless expression is the opposite of an if expression. It
executes code when a conditional is false.

Example 7
To check the number greater or lesser
a = 42
unless a < 10
puts "Yes“
else
puts "No“
end
Output:
Yes

Ruby unless modifier
SYNTAX
code unless conditional
• Note: Executes code if conditional is false.

Example 8
To check the number greater or lesser
using unless
a = 42
puts "Yes" if a > 10
puts "Yes" unless a < 10
Output:
Yes
Yes

Example 9
Using unless in multiple if
var = 1
print "1 -- Value is setn" if var
print "2 -- Value is setn" unless var
var = false
print "3 -- Value is setn" unless var
Output:
1 -- Value is set
3 -- Value is set

Ruby case Statement
SYNTAX
case expression
[when expression [, expression ...] [then]
code ]...
[else
code ]
end
Note that the case expression must be closed with the end keyword.

Example 10
To guess the age
age = 5
case age
when 1, 2, 3
puts "Little baby"
when 4, 5
puts "Child“
end
Output:
Child

Example 11
To guess the age using else
age = 18
case age
when 1, 2, 3
puts "Little baby"
when 4, 5
puts "Child"
else
puts “Adult“
end
Output:
Adult

LOOPS
• While
• Until
• Ranges
• For
• Loop break
• Loop next
• Loop do

While Statement
SYNTAX
while conditional [do]
code
end
Note: Executes code while conditional is true.

Example 12
x = 0
while x < 10
puts x
x += 1
end
0 1 2 3 4 5 6 7 8 9
CODE OUTPUT

Until Loops
SYNTAX
until conditional [do]
code
end
Note: Executes code while conditional is false

Example 13
a = 0
until a > 10
puts "a = #{a}"
a +=2
end
a = 0
a = 2
a = 4
a = 6
a = 8
a = 10
CODE OUTPUT

Ranges
a = (1..7).to_a
puts a
b = (79...82).to_a
puts b
c = ("a".."d").to_a
puts c
[1, 2, 3, 4, 5, 6, 7]
[79, 80, 81]
[a, b, c, d]
CODE OUTPUT

Example 14
age = 42
case age
when 0..14
puts "Child“
when 15..24
puts "Youth“
when 25..64
puts "Adult“
Else
puts "Senior“
end
Adult
CODE OUTPUT

For Loop
SYNTAX
for variable [, variable ...] in expression [do]
code
end
• Note: Executes code once for each element
in expression.

Example 15
for i in (1..10)
puts i
end
1 2 3 4 5 6 7 8 9 10
CODE OUTPUT

Example 16
for i in 1..5
break if i > 3
puts i
end
1
2
3
CODE OUTPUT

Example 17
for i in 0..10
next if i %2 == 0
puts i
End
Note: Next statement skip one
iteration
1 3 5 7 9
CODE OUTPUT

Example 18
x = 0
loop do
puts x
x += 1
break if x > 10
end
0 1 2 3 4 5 6 7 8 9 10
CODE OUTPUT

ARRAYS
• Creation
• Accessing
• Updating
• Adding
• Removing
• Ranges
• Manipulations

ARRAYS
SYNTAX
names = [item1,item2…item n]
Example
items = ["Apple", "Orange", "Banana"]
Note:
An Array is essentially a list of numbered items.

Accessing array elements
SYNTAX
puts array_name[index_value]
Example
puts items[0]
Note:
A negative index is assumed relative to the end of
the array. For example, an index of -1 indicates
the last element of the array.

Adding Elements
arr = [5, "Dave", 15.88, false]
puts arr[0]
puts arr[1]
puts arr[-1]
arr << 8
puts arr
arr.insert(2, 8)
5
Dave
false
5 Dave 15.88 false 8
5 Dave 8 15.88 false
CODE OUTPUT

Removing Elements
arr = [1, 2, 3]
arr.pop
print arr
arr = [2, 4, 6, 8]
arr.delete_at(2)
print arr
[1, 2]
[2, 4, 8]
CODE OUTPUT

Array Ranges
nums = [6, 3, 8, 7, 9]
print nums[1..3]
[3, 8, 7]
CODE OUTPUT

Array Manipulations
Joining two arrays
a = [1, 2, 3]
b = [4, 5]
res = a + b
print res
Removing elements present in both array
a = [1, 2, 3, 4, 5]
b = [2, 4, 5, 6]
res = a – b
print res
[1, 2, 3, 4, 5]
[1, 3]
CODE OUTPUT

Array Manipulations
Return common elements
a = [2, 3, 7, 8]
b = [2, 7, 9]
print a & b
Join array and remove
duplicates
a = [2, 3, 7, 8]
b = [2, 7, 9]
print a | b
[2, 7]
[2, 3, 7, 8, 9]
CODE OUTPUT

For loop to iterate
arr = ["a", "b", "c"]
for x in arr
puts "Value: #{x}“
end
Value: a
Value: b
Value: c
CODE OUTPUT

Hashes
Hashes (sometimes known as associative
arrays, maps, or dictionaries) are similar to
arrays in that they are an indexed collection
of elements.
Example:
ages = { "David" => 28, "Amy"=> 19, "Rob" => 42 }
puts ages["Amy"]

Examples
h = {"name"=>"Dave",
"age"=>28,
"gender"=>"male"}
puts h["age"]
28
CODE OUTPUT

Methods
SYNTAX
def method_name
code
end

Example 19
def say
puts "Hi"
end
say
Hi
CODE OUTPUT

Example 20
def sqr(x)
puts x*x
end
sqr(8)
64
CODE OUTPUT

Example 21
def sum(a, b)
puts a+b
end
sum(7, 4)
11
CODE OUTPUT

Example 22
def sum(a, b=8)
puts a+b
end
x = 5
sum(x)
Note: You can also set default
values for the parameters, so
that the method will still work
even if you do not provide all
the arguments.
13
CODE OUTPUT

Example 21
def greet(name="")
if name==""
puts "Greetings!"
else
puts "Welcome,
#{name}"
end
end
greet(gets.chomp)
Welcome, hi
CODE OUTPUT

Example 22
def someMethod(*p)
puts p
end
someMethod(25, "hello", true)
25 hello true
CODE OUTPUT

BLOCKS
A block is always invoked from a function with the
same name as that of the block.
SYNTAX
block_name
{
statement1
statement2
..........
}

Example 23
def test
yield
end
test{ puts "Hello world"}
Hello world
CODE OUTPUT

Example 24
def test
puts "You are in the method"
yield
puts "You are again back to
the method"
yield
end
test {puts "You are in the
block"}
You are in the method
You are in the block
You are again back to the
method
You are in the block
CODE OUTPUT

Example 25
def test
yield 5
puts "You are in the method
test"
yield 100
end
test {|i| puts "You are in the
block #{i}"}
You are in the block 5
You are in the method test
You are in the block 100
CODE OUTPUT

Example 23
def test(&block)
block.call
end
test { puts "Hello World!"}
Hello world
CODE OUTPUT

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