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I am trying to create a nested hash where the inner values are arrays. For example
{"monday"=>{"morning"=>["John", "Katie", "Dave"],"afternoon"=>["Anne", "Charlie"]},
"tuesday"=>{"morning"=>["Joe"],"afternoon"=>["Chris","Tim","Melissa"]}}
I tried
h = Hash.new( |hash, key| hash[key] = Hash.new([]) }
When I try
h["monday"]["morning"].append("Ben")
and look at h, I get
{"monday" => {}}
rather than
{"monday" => {"morning"=>["Ben"]}}
I'm pretty new to Ruby, any suggestions for getting the functionality I want?
Close, you'll have to initialise a new hash as the value of the initial key, and set an Array as the value of the nested hash:
h = Hash.new { |hash, key| hash[key] = Hash.new { |k, v| k[v] = Array.new } }
h["monday"]["morning"] << "Ben"
{"monday"=>{"morning"=>["Ben"]}}
This way you will not have to initialise an array every time you want to push a value. The key will be as you set in the initial parameter, the second parameter will create a nested hash where the value will be an array you can push to with '<<'. Is this a solution to use in live code? No, it’s not very readable but explains a way of constructing data objects to fit your needs.
Refactored for Explicitness
While it's possible to create a nested initializer using the Hash#new block syntax, it's not really very readable and (as you've seen) it can be hard to debug. It may therefore be more useful to construct your nested hash in steps that you can inspect and debug as you go.
In addition, you already know ahead of time what your keys will be: the days of the week, and morning/afternoon shifts. For this use case, you might as well construct those upfront rather than relying on default values.
Consider the following:
require 'date'
# initialize your hash with a literal
schedule = {}
# use constant from Date module to initialize your
# lowercase keys
Date::DAYNAMES.each do |day|
# create keys with empty arrays for each shift
schedule[day.downcase] = {
"morning" => [],
"afternoon" => [],
}
end
This seems more explicit and readable to me, but that's admittedly subjective. Meanwhile, calling pp schedule will show you the new data structure:
{"sunday"=>{"morning"=>[], "afternoon"=>[]},
"monday"=>{"morning"=>[], "afternoon"=>[]},
"tuesday"=>{"morning"=>[], "afternoon"=>[]},
"wednesday"=>{"morning"=>[], "afternoon"=>[]},
"thursday"=>{"morning"=>[], "afternoon"=>[]},
"friday"=>{"morning"=>[], "afternoon"=>[]},
"saturday"=>{"morning"=>[], "afternoon"=>[]}}
The new data structure can then have its nested array values assigned as you currently expect:
schedule["monday"]["morning"].append("Ben")
#=> ["Ben"]
As a further refinement, you could append to your nested arrays in a way that ensures you don't duplicate names within a scheduled shift. For example:
schedule["monday"]["morning"].<<("Ben").uniq!
schedule["monday"]
#=> {"morning"=>["Ben"], "afternoon"=>[]}
There are many ways to create the hash. One simple way is as follows.
days = [:monday, :tuesday]
day_parts = [:morning, :afternoon]
h = days.each_with_object({}) do |d,h|
h[d] = day_parts.each_with_object({}) { |dp,g| g[dp] = [] }
end
#=> {:monday=>{:morning=>[], :afternoon=>[]},
# :tuesday=>{:morning=>[], :afternoon=>[]}}
Populating the hash will of course depend on the format of the data. For example, if the data were as follows:
people = { "John" =>[:monday, :morning],
"Katie" =>[:monday, :morning],
"Dave" =>[:monday, :morning],
"Anne" =>[:monday, :afternoon],
"Charlie"=>[:monday, :afternoon],
"Joe" =>[:tuesday, :morning],
"Chris" =>[:tuesday, :afternoon],
"Tim" =>[:tuesday, :afternoon],
"Melissa"=>[:tuesday, :afternoon]}
we could build the hash as follows.
people.each { |name,(day,day_part)| h[day][day_part] << name }
#=> {
# :monday=>{
# :morning=>["John", "Katie", "Dave"],
# :afternoon=>["Anne", "Charlie"]
# },
# :tuesday=>{
# :morning=>["Joe"],
# :afternoon=>["Chris", "Tim", "Melissa"]
# }
# }
As per your above-asked question
h = Hash.new{ |hash, key| hash[key] = Hash.new([]) }
you tried
h["monday"]["morning"].append("Ben")
instead you should first initialize that with an array & then you can use array functions like append
h["monday"]["morning"] = []
h["monday"]["morning"].append("Ben")
This would work fine & you will get the desired results.
I have a hash looks like :
response = {
data: {
target_file: "file.jpg"
}
}
and have a string "data.target_file"
What I want is how can I access target_file value based on that string, like accessing with response[:data][:target_file]
how can I convert as dinamically from string "data.target_file" to response[:data][:target_file]
so I don't want use something like response["#{string.split('.')[0]}".to_sym]["#{string.split('.')[1]}".to_sym]
You can use split like you've shown to convert the keys into a string array, then map the strings into symbols and finally dig the hash whilst extracting the array elements as arguments with the splat operator *:
response.dig(*"data.target_file".split(".").map(&:to_sym))
If you see yourself repeating this code, you can extend the Hash class and add a method that does it:
class Hash
def dot(path)
self.dig(*path.split(".").map(&:to_sym))
end
end
Then you would simply use:
response.dot("data.target_file")
I have data in the format:
data={"services"=>[{"name"=>"foo","checks"=>["script1","script2"]},
{"name"=>"bar","checks"=>["script3"]}]}
I am trying to replace "checks" for each check to be "/bin/#{check}". The code I was playing with is
data["services"].map! {|svc|
svc["checks"].map! {|check|
check = "/bin/#{check}"
}
}
But this code replaces the whole service hash instead of just one key, and I get:
{"services"=>[["/bin/script1", "/bin/script2"], ["/bin/script3"]]}
Can I use map! in deeply nested arrays of hashes of arrays of... ? Or how else can I do what I need?
I suggest avoiding changing data and just return a new hash:
new_data = data.each_with_object({}) do |(service, values), hash|
hash[service] = values.map do |value|
checks = value['checks'].map { |check| "/bin/#{check}" }
value.merge('checks' => checks)
end
end
=> {"services"=>[{"name"=>"foo", "checks"=>["/bin/script1", "/bin/script2"]}, {"name"=>"bar", "checks"=>["/bin/script3"]}]}
I'm trying to get the index of a key in a hash.
I know how to do this in an array:
arr = ['Done', 13, 0.4, true]
a = arr.index('Done')
puts a
Is there a method or some sort of way to do this something like this with a key in a hash? Thanks!
Hashes aren't usually treated as ordered structures, they simply have a list of keys and values corresponding to those keys.
It's true that in Ruby hashes are technically ordered, but there's very rarely an actual use case for treating them as such.
If what you want to do is find the key corresponding to a value in a hash, you can simply use the Hash#key method:
hash = { a: 1, b: 2 }
hash.key(1) # => :a
I suppose you could use hash.keys.index(hash.key(1)) to get 0 since it's the first value, but again, I wouldn't advise doing this because it's not typical use of the data structure
There are at least a couple ways you can get this information, the 2 that come to mind are Enumerable's find_index method to pass each element to a block and check for your key:
hash.find_index { |key, _| key == 'Done' }
or you could get all the keys from your hash as an array and then look up the index as you've been doing:
hash.keys.index('Done')
I have been using Ruby for a while, but this is my first time doing anything with a database. I've been playing around with MongoDB for a bit and, at this point, I've begun to try and populate a simple database.
Here is my problem. I have a text file containing data in a particular format. When I read that file in, the data is stored in nested arrays like so:
dataFile = ["sectionName", ["key1", "value1"], ["key2", "value2", ["key3", ["value3A", "value3B"]]]
The format will always be that the first value of the array is a string and each subsequent value is an array. Each array is formatted in as a key/value pair. However, the value can be a string, an array of two strings, or a series of arrays that have their own key/value array pairs. I don't know any details about the data file before I read it in, just that it conforms to these rules.
Now, here is my problem. I want to read this into to a Mongo database preserving this basic structure. So, for instance, if I were to do this by hand, it would look like this:
newDB = mongo_client.db("newDB")
newCollection = newDB["dataFile1"]
doc = {"section_name" => "sectionName", "key1" => "value1", "key2" => "value2", "key3" => ["value3A", "value3B"]}
ID = newCollection.insert(doc)
I know there has to be an easy way to do this. So far, I've been trying various recursive functions to parse the data out, turn it into mongo commands and try to populate my database. But it just feels clunky, like there is a better way. Any insight into this problem would be appreciated.
The value that you gave for the variable dataFile isn't a valid array, because it is missing an closing square bracket.
If we made the definition of dataFile a valid line of ruby code, the following code would yield the hash that you described. It uses map.with_index to visit each element of the array and transforms this array into a new array of key/value hashes. This transformed array of hashes is flatted and converted into single hash using the inject method.
dataFile = ["sectionName", ["key1", "value1"], ["key2", "value2", ["key3", ["value3A", "value3B"]]]]
puts dataFile.map.with_index {
|e, ix|
case ix
when 0
{ "section_name" => e }
else
list = []
list.push( { e[0] => e[1] } )
if( e.length > 2 )
list.push(
e[2..e.length-1].map {|p|
{ p[0] => p[1] }
}
)
end
list
end
}.flatten.inject({ }) {
|accum, e|
key = e.keys.first
accum[ key ] = e[ key ]
accum
}.inspect
The output looks like:
{"section_name"=>"sectionName", "key1"=>"value1", "key2"=>"value2", "key3"=>["value3A", "value3B"]}
For input that looked like this:
["sectionName", ["key1", "value1"], ["key2", "value2", ["key3", ["value3A", "value3B"]], ["key4", ["value4A", "value4B"]]], ["key5", ["value5A", "value5B"]]]
We would see:
{"section_name"=>"sectionName", "key1"=>"value1", "key2"=>"value2", "key3"=>["value3A", "value3B"], "key4"=>["value4A", "value4B"], "key5"=>["value5A", "value5B"]}
Note the arrays "key3" and "key4", which is what I consider as being called a series of arrays. If the structure has array of arrays of unknown depth then we would need a different implementation - maybe use an array to keep track of the position as the program walks through this arbitrarily nested array of arrays.
In the following test, please find two solutions.
The first converts to a nested Hash which is what I think that you want without flattening the input data.
The second stores the key-value pairs exactly as given from the input.
I've chosen to fix missing closing square bracket by preserving key values pairs.
The major message here is that while the top-level data structure for MongoDB is a document mapped to a Ruby Hash
that by definition has key-value structure, the values can be any shape including nested arrays or hashes.
So I hope that test examples cover the range, showing that you can match storage in MongoDB to fit your needs.
test.rb
require 'mongo'
require 'test/unit'
require 'pp'
class MyTest < Test::Unit::TestCase
def setup
#coll = Mongo::MongoClient.new['test']['test']
#coll.remove
#dataFile = ["sectionName", ["key1", "value1"], ["key2", "value2"], ["key3", ["value3A", "value3B"]]]
#key, *#value = #dataFile
end
test "nested array data as hash value" do
input_doc = {#key => Hash[*#value.flatten(1)]}
#coll.insert(input_doc)
fetched_doc = #coll.find.first
assert_equal(input_doc[#key], fetched_doc[#key])
puts "#{name} fetched hash value doc:"
pp fetched_doc
end
test "nested array data as array value" do
input_doc = {#key => #value}
#coll.insert(input_doc)
fetched_doc = #coll.find.first
assert_equal(input_doc[#key], fetched_doc[#key])
puts "#{name} fetched array doc:"
pp fetched_doc
end
end
ruby test.rb
$ ruby test.rb
Loaded suite test
Started
test: nested array data as array value(MyTest) fetched array doc:
{"_id"=>BSON::ObjectId('5357d4ac7f11ba0678000001'),
"sectionName"=>
[["key1", "value1"], ["key2", "value2"], ["key3", ["value3A", "value3B"]]]}
.test: nested array data as hash value(MyTest) fetched hash value doc:
{"_id"=>BSON::ObjectId('5357d4ac7f11ba0678000002'),
"sectionName"=>
{"key1"=>"value1", "key2"=>"value2", "key3"=>["value3A", "value3B"]}}
.
Finished in 0.009493 seconds.
2 tests, 2 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
210.68 tests/s, 210.68 assertions/s