Iterate through an array and push elements into individual new arrays - arrays

Question

I have an array:
["apple", "banana", "animal", "car", "angel"]
I want to push elements that start with "a" into separate arrays. I want to return:
["apple"], ["animal"], ["angel"]
I have only been able to make it work if I push them into an empty array that I pre-created.

Answer 1

Generally in order to pick elements from array that match some specific conditione use select method.
select returns an array of all elements that matched critera or an empty list in case neither element has matched
example:
new_array = array.select do |element|
return_true_or_false_depending_on_element(element)
end
now when we would like to put every element in its own array we could you another array method that is available on array - map which takes every element of an array and transforms it in another element. In our case we will want to take every matching string and wrap it in array
map usage:
new_array = array.map do |element|
element_transformation(element) # in order to wrap element just return new array with element like this: [element]
end
coming back to your question. in order to verify whether a string starts with a letter you could use start_with? method which is available for every string
glueing it all together:
strings = ["apple", "banana", "animal", "car", "angel"]
result = strings.select do |string|
string.start_with?("a")
end.map do |string_that_start_with_a|
[string_that_start_with_a]
end
puts result

Answer 2

Here's a golfed down version:
array.grep(/\Aa/).map(&method(:Array))
I might consider my audience before putting something this clever into production, since it can be a little confusing.
Array#grep returns all elements that match the passed regular expression, in this case /\Aa/ matches strings that begin with a. \A is a regular expression token that matches the beginning of the string. You could change it to /\Aa/i if you want it to be case insensitive.
The &method(:Array) bit grabs a reference to the kernel method Array() and runs it on each element of the array, wrapping each element in the array in its own array.

Answer 3

The simplest I can come up with is:
arr = %w{ apple banana animal car angel }
arr.map {|i| i.start_with?('a') ? [i] : nil }.compact
=> [["apple"], ["animal"], ["angel"]]

Answer 4

Here is some code I got to do this in console:
> arr = ["apple", "banana", "animal", "car", "angel"]
=> ["apple", "banana", "animal", "car", "angel"]
> a_words = []
=> []
arr.each do |word|
a_words << word if word.chars.first == 'a'
end
=> ["apple", "banana", "animal", "car", "angel"]
> a_words
=> ["apple", "animal", "angel"]
If you wanted to do something more complex than first letter you might want to use a regex like:
if word.matches(/\Aa/) # \A is beginning of string

Answer 5

array_of_arrays = []
your_array.each do |ele|
if ele.starts_with?("a")
array_of_arrays << ele.to_a
end
end