Sequentially parse array to hash in Ruby - ruby

Question

I have an array that looks like this:
array = [
"timestamp 1",
"data 1",
"data 2",
"data 3",
"timestamp 2",
"data "1",
"timestamp 3",
".."
]
etc
I want to loop through my array, and turn it into a hash data structure that looks like:
hash = {
"timestamp 1" => [ "data 1", " data 2", "data 3" ],
"timestamp 2" => [ "data 1" ],
}
I can't figure out a good "rubyish" way of doing it. I'm looping through the array, and I just quite can't seem to figure out how to keep track of where I am at, and assign to the hash as needed.
# Let's comb through the array, and map the time value to the subsequent lines beneath
array.each do |e|
if timestamp?(e)
hash["#{e}"] == nil
else
# last time stamp here => e
end
EDIT: Here is the timestamp? method
def timestamp?(string)
begin
return true if string =~ /[a-zA-z][a-z][a-z]\s[a-zA-z][a-z][a-z]\s\d\d\s\d\d:\d\d:\d\d\s\d\d\d\d/
false
rescue => msg
puts "Error in timestamp? => #{msg}"
exit
end
end

Answer 1

array = [
"timestamp 1",
"data 1",
"data 2",
"data 3",
"timestamp 2",
"data 1",
"timestamp 3",
"data 2"
]
hsh = {}
ary = []
array.each do |line|
if line.start_with?("timestamp")
ary = Array.new
hsh[line] = ary
else
ary << line
end
end
puts hsh.inspect

Answer 2

I would do as below:
array = [
"timestamp 1",
"data 1",
"data 2",
"data 3",
"timestamp 2",
"data 1",
]
Hash[array.slice_before{|i| i.include? 'timestamp'}.map{|a| [a.first,a[1..-1]]}]
# => {"timestamp 1"=>["data 1", "data 2", "data 3"], "timestamp 2"=>["data 1"]}

Answer 3

Hash[array.slice_before{|e| e.start_with?("timestamp ")}.map{|k, *v| [k, v]}]
Output
{
"timestamp 1" => [
"data 1",
"data 2",
"data 3"
],
"timestamp 2" => ["data 1"],
"timestamp 3" => [".."]
}

Answer 4

You can keep track of the last hash key using an outside variable. It will be persisted across all iterations:
h = {}
last_group = nil
array.each do |e|
if timestamp?(e)
array[e] = []
last_group = e
else
h[last_group] << e
end
end

Answer 5

last_timestamp = nil
array.reduce(Hash.new(){|hsh,k| hsh[k]=[]}) do |hsh, m|
if m =~ /timestamp/
last_timestamp = m
else
hsh[last_timestamp] << m
end
hsh
end

Answer 6

hash = (Hash.new { |this, key| this[key] = [] } ).tap do |hash|
current_timestamp = nil
array.each do |element|
current_timestamp = element if timestamp? element
hash[current_timestamp] << element unless timestamp? element
end
end
Using an outside variable to keep track of the current timestamp, but wrapping it in a closure to avoid polluting the namespace.

Answer 7

I know this has already been answered, but there are so many ways to do this.
I prefer these two ways, they might not be fast but i find them readable:
my_hash = Hash.new
array.slice_before(/timestamp/).each do |array|
key, *values = array
my_hash[key] = values
end
or
one_liner = Hash[array.slice_before(/timestamp/).map{|x|[x.shift, x]}]