Rubyのブロックとパラメータ渡しを説明する

(1..4).each{|v| print "#{v} "} #output 1 2 3 4 

sum = 0 
(1..5).each do |v| 
  name = 'smile' #name is an in-block variable and can only be seen inside the block. Assume there are no variables with the same name outside the block. 
  sum += v #sum is visible inside the block 
end 
p sum #output 15, sum has changed. 
p name #Error! name is not accessible. 

name = 'outside' 
sum = 0 
(1..5).each do |v;name| #name after ";", multiple variables can be declared, separated by commas 
  name = 'inside' #name is an in-block variable and can only be seen inside the block. Assume that there are no variables with the same name outside the block. 
  sum += v #sum is accessible within the block 
end 
p sum #output 15, sum has changed. 
p name #output outside, no change. 

def threeTime 
  yield 
  yield 
  yield 
end 
threeTime{p 'Hello world!} 

def takeBlock(p1) 
 if block_given? # Determine if there is a block, if there is no block declared at yield, there will be an error, so it is better to make the determination here. 
  yield(p1) # pass p1 to the block argument, both the s in the block declaration below 
 else 
  p1 
 end 
endie 
 
takeBlock("no block") # output "no block" 
takeBlock("no block") { |s| s.sub(/no /, '') } #output"block" 

def nTime 
 i = yield # The first time it is called, the value of the block is returned 
 (0..i).each {|v| yield(v)} # Here yield can also be placed in the block 
end 
nTime do |v| 
 print "#{v} " if v 
 9 # The number returned when the yield is called 
end 
#output 1 2 3 4 5 6 7 8 9 

def nTime(n) 
 (0..n).each {|v| yield(v)} 
end 
nTime(9) do |v| 
 print "#{v} " 
end 

class Array 
 def find 
  for i in 0... .size 
   value = self[i] 
   return value if yield(value) 
  end 
  return nil 
 end 
end 
[1, 3, 5, 7, 9].find {|v| v > 5 } # Implement find the first number greater than 5, output 7.

def fun #without arguments 
 yield 
end 
proc = ->{p 'haha'} 
 
fun &proc 
##### 
def fun2(x) # with arguments 
 yield x 
end 
proc2 = ->(x){p x} 
fun2 1,&proc2 

class MyClass 
 def initialize 
  @v = 1; 
 end 
end 
obj = MyClass.new 
obj.instance_eval do 
 puts self # => #<MyClass:0x007fbb2d0299b0> 
 puts @v # => 1 
end 
obj.instance_exec(5) { |x| puts x * @v } # => 5