Merge Arrays in Ruby/Rails

Merge arrays in Ruby/Rails

Like this?

⚡️ irb
2.2.2 :001 > [1,2,3] + [4,5,6]
 => [1, 2, 3, 4, 5, 6] 

But you don't have 2 arrays.

You could do something like:

@movie = Movie.first()
@options = Movie.order("RANDOM()").first(3).to_a << @movie

How to merge two array objects in ruby?

array1 = [{ID:"1",name:"Dog"}]
array2 = [{ID:"2",name:"Cat"}]
p array1 + array2
# => [{:ID=>"1", :name=>"Dog"}, {:ID=>"2", :name=>"Cat"}]

Or maybe this is superfluous:

array1 = [{ID:"1",name:"Dog"}]
array2 = [{ID:"2",name:"Cat"}]
array3 = [{ID:"3",name:"Duck"}]

p [array1, array2, array3].map(&:first)
# => [{:ID=>"1", :name=>"Dog"}, {:ID=>"2", :name=>"Cat"}, {:ID=>"3", :name=>"Duck"}]

Merge array at specific index in Ruby

You can use the normal element assignment, Array#[]= and pass in the start and length parameters:

Element Assignment — Sets the element at index, or replaces a subarray from the start index for length elements, or replaces a subarray specified by the range of indices.

(emphasis mine) So, for instance:

@a1 = [0,0,0,0,0]
a2 = [1,1]
@a1[1, a2.length] = a2
@a1 # => [0, 1, 1, 0, 0]
@a1 = [0,0,0,0,0]
@a1[@a1.length - a2.length, a2.length] = a2
@a1 # => [0, 0, 0, 1, 1]

How to merge an array of arrays together into a single array?

[["convertible", "2010", "red"], ["convertible", "2010", "green"]].flatten!

Array of arrays merge in Rails

You could use Hash#merge! method with a block for that:

initial = [['Area1', 12345], ['Area2', 54321]].to_h
initial.merge!({'Area1' => 1212 }) { |_,v1,v2| [v1,v2].flatten }
#=> {"Area1"=>[12345, 1212], "Area2"=>54321}

and if you want the result to be an array, you can use

initial.merge!({'Area1' => 1212 }) { |_,v1,v2| [v1,v2].flatten }.to_a

Merge and interleave two arrays in Ruby

You can do that with:

a.zip(s).flatten.compact

Ruby - Merge two arrays and remove values that have duplicate

You can do the following!

# Merging
c = a + b
 => [1, 2, 3, 4, 5, 2, 4, 6]
# Removing the value of other array
# (a & b) is getting the common element from these two arrays
c - (a & b)
=> [1, 3, 5, 6]

Dmitri's comment is also same though I came up with my idea independently.

How to add and merge values from different array of hashes in ruby on rails

Using two helper methods for a DRY code and using Enumerable#sum, Enumerable#group_by, Hash#merge, Hash#transform_values and also other methods you can find in the documentation.

I'm using also Object#then here.

def sum_price_tax(ary)
  ary.first.merge ary.then { |ary| { "Price" => ary.sum { |h| h["Price"].to_f }, "Tax" => ary.sum { |h| h["Tax"].to_f} }  }
end

def group_and_sum(array_of_hash)
  array_of_hash.group_by { |h| h["Date"] }.transform_values { |ary| sum_price_tax(ary) }
end

After the methods are defined, you can do:

a1 = group_and_sum(array_of_hash1)
a2 = group_and_sum(array_of_hash2)
a1.map { |k, v| v.merge(a2[k] || {}) { |h, old_val, new_val| old_val.is_a?(Float) ? old_val - new_val : old_val  } }

#=> [{"Date"=>"2019-07-01", "Country"=>"US", "Email"=>"sample1@gmail.com", "Price"=>2.2121007000000006, "Tax"=>6.254, "Name"=>"John"}, {"Date"=>"2019-06-30", "Country"=>"US", "Email"=>"sample3@gmail.com", "Price"=>17.854323, "Tax"=>7.12343}, {"Date"=>"2019-07-02", "Country"=>"UK", "Email"=>"sample4@gmail.com", "Price"=>4.0019787, "Tax"=>1.9798780000000002, "Name"=>"Sam"}]

In this way also the "Name" is present.

---

One way you could get rid of "Name" is using Object#tap and Hash#delete:

a1.map { |k, v| v.merge(a2[k] || {}) { |h, old_val, new_val| old_val.is_a?(Float) ? old_val - new_val : old_val  }.tap { |h| h.delete("Name") } }

#=> [{"Date"=>"2019-07-01", "Country"=>"US", "Email"=>"sample1@gmail.com", "Price"=>2.2121007000000006, "Tax"=>6.254}, {"Date"=>"2019-06-30", "Country"=>"US", "Email"=>"sample3@gmail.com", "Price"=>17.854323, "Tax"=>7.12343}, {"Date"=>"2019-07-02", "Country"=>"UK", "Email"=>"sample4@gmail.com", "Price"=>4.0019787, "Tax"=>1.9798780000000002}]

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