Reading notes on looping and iteration from the sixth chapter (Control-flow techniques) of The Well-Grounded Rubyist by David A. Black.
loop method
For one line of code use curly braces:
loop { # One line of code here }For multi-lines use do..end:
i = 0
loop do
puts i += 1
break if i > 9
endOr
i = 0
loop do
puts i += 1
next unless i == 10
break
end
while keyword
i = 0
while i < 10
puts i += 1
endOr
i = 0
begin
puts i += 1
end while i < 10Or
i = 0
puts i += 1 while i < 10
until keyword
i = 0
until i > 9
puts i += 1
endOr
i = 0
begin
puts i += 1
end until i > 9Or
i = 0
puts i += 1 until i > 9
for keyword
nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for i in nums
puts i
end
times iterator
code = ?a.ord - 1
p 10.times {puts (code += 1).chr}The code snippets above will output: a to j AND return 10 (the number of times we’ve iterated the code block).
code = ?a.ord
p 10.times {|i| puts (code + i).chr}Note that block parameters are inside vertical pipes.
each method
array = [1,2,3,4,5]
p array.each {|i| puts "I'm No #{i}"}Output:
I'm No 1
I'm No 2
I'm No 3
I'm No 4
I'm No 5
[1, 2, 3, 4, 5]
Implementing each:
class Array
# Extend Ruby's Array class with a custom each method:
def test_each
i = 0
until i == size
yield(self[i])
i += 1
end
self
end
end
array = [1,2,3,4,5]
array.test_each {|num| puts "I'm No #{num}"}
Converting a Range to an Array
upper = 5
array = (1..upper).to_a
p array
map method
array = ["bill", "bob", "ben"]
p array.map {|name| name.upcase}Output:
["BILL", "BOB", "BEN"]
Code block reserved names
def block_local_variable
x = "Original x!"
3.times do |i;x|
x = i
puts "x in the block is now #{x}."
end
puts "x after the block ended is #{x}"
end
block_local_variable=> Use a semicolon in the block parameter list to indicate that we want to use a variable named x (the reserved name) that is local to the code block.