How to get a specific output iterating a hash in Ruby?

Question

I want to get a specific output iterating a Ruby Hash.

This is the Hash I want to iterate over:

hash = {
  1 => ['a', 'b'], 
  2 => ['c'], 
  3 => ['d', 'e', 'f', 'g'], 
  4 => ['h']
}

This is the output I would like to get:

1-----

a

b

2-----

c

3-----

d 

e

f

g

4-----

h

In Ruby, how can I get such an output with my Hash ?

Solution 1

hash.each do |key, array|
  puts "#{key}-----"
  puts array
end

Regarding order I should add, that in 1.8 the items will be iterated in random order (well, actually in an order defined by Fixnum's hashing function), while in 1.9 it will be iterated in the order of the literal.

Solution 2

The most basic way to iterate over a hash is as follows:

hash.each do |key, value|
  puts key
  puts value
end

Solution 3

hash.keys.sort.each do |key|
  puts "#{key}-----"
  hash[key].each { |val| puts val }
end

Solution 4

Calling sort on a hash converts it into nested arrays and then sorts them by key, so all you need is this:

puts h.sort.map {|k,v| ["#{k}----"] + v}

And if you don't actually need the "----" part, it can be just:

puts h.sort

Solution 5

My one line solution:

hash.each { |key, array| puts "#{key}-----", array }

I think it is pretty easy to read.

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Comments

[Allen Rice]

If you're iterating a hash and expecting it to be ordered, you probably need to use some other collection type

[glenn jackman]

The hash keys are numbers, so '[k + "----"]' raises a TypeError (String can't be coerced into Fixnum). You need '[k.to_s + "----"]'

[mashe]

True enough. I had letters in my test version. Fixed, using the even better "#{k}----".

[huzefa biyawarwala]

here what if key isn't used anywhere ? . do we need to put a ? in place of key ? ex : |?, array| is this valid syntax ?

[sepp2k]

@huzefabiyawarwala No, ? is not a valid variable name in Ruby. You can use _, but you don't need to.

[huzefa biyawarwala]

what i meant was if we use |k,v| for iterating over a hash, but we don't use k in our logic implementation inside our loop, so is there any way we can write like this |_, v| ?

[sepp2k]

@huzefabiyawarwala Yes, you can write |_, v|

[jrhicks]

what use variable name array instead of v or value?

[Radon Rosborough]

@jrhicks Because the OP has a hash whose values are arrays.