what's different between each and collect method in Ruby

ruby each collect
mko picture mko · Mar 18, 2011 · Viewed 56.3k times · Source

From this code I don't know the difference between the two methods, collect and each.

a = ["L","Z","J"].collect{|x| puts x.succ} #=> M AA K 
print  a.class  #=> Array

b = ["L","Z","J"].each{|x| puts x.succ} #=> M AA K
print  b.class #=> Array

Answer

RameshVel picture RameshVel · Mar 18, 2011

Array#each takes an array and applies the given block over all items. It doesn't affect the array or creates a new object. It is just a way of looping over items. Also it returns self.

  arr=[1,2,3,4]
  arr.each {|x| puts x*2}

Prints 2,4,6,8 and returns [1,2,3,4] no matter what

Array#collect is same as Array#map and it applies the given block of code on all the items and returns the new array. simply put 'Projects each element of a sequence into a new form'

  arr.collect {|x| x*2}

Returns [2,4,6,8]

And In your code

 a = ["L","Z","J"].collect{|x| puts x.succ} #=> M AA K

a is an Array but it is actually an array of Nil's [nil,nil,nil] because puts x.succ returns nil (even though it prints M AA K).

And 

 b = ["L","Z","J"].each{|x| puts x.succ} #=> M AA K

also is an Array. But its value is ["L","Z","J"], because it returns self.

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