Ruby - Array Appending vs. Concatenating
Introduction
Concatenating using + adds the values from the second array to the first.
Appending using << adds the second array itself as the final element of the first:
Demo
a =[1,2,3] b =[4,5,6] # w w w. j av a2 s . c om c = a + b #=> c=[1, 2, 3, 4, 5, 6] a=[1, 2, 3] puts c a << b #=> a=[1, 2, 3, [4, 5, 6]] puts a
Result
<< modifies the first (the receiver) array, whereas + returns a new array but leaves the receiver array unchanged.
You can use the flatten method to clean up two arrays you've combined with <<, like this:
Demo
a=[1, 2, 3, [4, 5, 6]]
puts a.flatten #=> [1, 2, 3, 4, 5, 6]
Result
