A loop is a control structure that allows you to repeatedly execute a block of code.
loop do
puts "I'm looping..."
end
Loops 🔗
The above code is called an infinite loop because it won’t stop executing unless we add a clause.
20.times do
puts "I'm looping..."
end
I'm looping...
I'm looping...
I'm looping...
.......
.......
I'm looping... (20th)
We could also do
1.upto(20) do
puts "I'm looping..."
end
Also
1.upto(10) { |n| puts n }
While Loop 🔗
while <= 50
puts "Not greater than or equals to 50, yet..."
num += 1
end
Until Keyword 🔗
until num > 50
puts "Not there yet..."
num += 1
end
.each 🔗
nums = [1, 2, 3, 4, 5]
nums.each { |num| puts num}
output:
1
2
3
4
5
Code Blocks 🔗
They are nameless methods. They can be passed into other methods or stored for later use.
negative_nums = [-1, -2, -3, -4, -5]
positive_nums = negative_nums { |num| mum.abs}
output:
[1, 2, 3, 4, 5]
Code blocks can also be passed into methods for reusability. Each method call below will produce a different result.
def play_with_each_toy(toy_box, &instructions)
toy_box.each do |toy|
instructions.call(toy)
end
end
toys = [1, 2, 3, 4, 5]
play_with_each_toy(toys) do |toy|
puts toy * 2
end
play_with_each_toy(toys) do |toy|
puts toy * 4
end
We could also use the yield keyword to achieve the same result
def play_with_each_toy(toy_box)
toy_box.each do |toy|
yield(toy * 2)
end
end
toys = [1, 2, 3, 4, 5]
play_with_each_toy(toys) do |result|
puts result
end
Also, we could save a block for later use
saved_block = Proc.new { |x| x * 3 }
result = saved_block.call(5)
puts "Result from saved block: #{result}"
if block_given? 🔗
Calling a blocked method without a block will return an error. Even with using the yield keyword. We solve this using a conditional
def play_with_each_toy(toy_box, &instructions)
toy_box.each do |toy|
instructions.call(toy) if block_given?
end
end
toys = [1, 2, 3, 4, 5]
# Using the block
play_with_each_toy(toys) do |toy|
puts toy * 3
end
# Without providing a block
play_with_each_toy(toys)
We can also create a code block with lambda and stubby_lambda
# Using lambda keyword
my_lambda = lambda { |x| puts x * 2 }
my_lambda.call(5) # Output: 10
# Using stabby lambda syntax
my_stabby_lambda = ->(x) { puts x * 2 }
my_stabby_lambda.call(5) # Output: 10
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