02 - binding a block argument to a variable.rb

来自「O Reilly Ruby Cookbook source code」· RB 代码 · 共 59 行

def repeat(n)
  n.times { yield } if block_given?
end
repeat(2) { puts "Hello." }
# Hello.
# Hello.


def repeat(n, &block)
  n.times { block.call } if block
end
repeat(2) { puts "Hello." }
# Hello.
# Hello.

def repeat(n, &block)
  n.times { yield } if block
end
repeat(2) { puts "Hello." }
# Hello.
# Hello.
#---
def biggest(collection, &block)
  block ? collection.select(&block).max : collection.max
end

array = [1, 2, 3, 4, 5]
biggest(array) {|i| i < 3}                   # => 2
biggest(array) {|i| i != 5 }                 # => 4
biggest(array)                               # => 5
#---
def pick_random_numbers(min, max, limit)
  limit.times { yield min+rand(max+1) }
end

#---
def lottery_style_numbers(&block)
  pick_random_numbers(1, 49, 6, &block)
end

lottery_style_numbers { |n| puts "Lucky number: #{n}" }
# Lucky number: 20
# Lucky number: 39
# Lucky number: 41
# Lucky number: 10
# Lucky number: 41
# Lucky number: 32
#---
def invoke_on_each(*args, &block)
  args.each { |arg| yield arg }
end

invoke_on_each(1, 2, 3, 4) { |x| puts x ** 2 }
# 1
# 4
# 9
# 16
#---