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my request returns any type of JSON. I would like to give a key to each attribute recursively in Ruby.
{
"name": "My name",
"age": 17,
"users": [
{
"name": "John Doe",
"colours": [
"blue",
"red"
],
"animals": [
{
"name": "Panthera"
}
]
}
]
}
It should traverse the tree and return:
[ 'name', 'age', 'users[]' 'users[]name', 'users[]colours', 'users[]animals', users[]animals[]name' ]
I can get top-level keys by calling Hash.keys but not sure how to traverse the tree and return custom key. Thanks for your help.
j = {"name":"My name","age":17,"users":[{"name":"John Doe","colours":["blue","red"],"animals":[{"name":"Panthera"}]}]}
a = []
j.keys.each do |key|
if key.class == Array
a << "#{key}[]"
else
a << key
end
end
a
This seems to achieve what you want. You were on the right track thinking recursively. I added comments to explain what's happening.
require 'json'
# Convert JSON to a ruby hash
j = JSON.parse('{"name":"My name","age":17,"users":[{"name":"John Doe","colours":["blue","red"],"animals":[{"name":"Panthera"}]}]}')
a = []
def make_array_from_hash_keys(array, hash, prefix = "")
# Iterate through the hash's key/value pairs
hash.each do |key, value|
# If the value is an array, we set a new prefix and add that to the main
# array. Then we iterate through this inner array to see if there are more
# hashes. If there are, call the parent method to generate more elements
# for the array, using the new prefix.
if value.class == Array
new_prefix = "#{prefix + key}[]"
array << new_prefix
hash[key].each do |array_value|
if array_value.class == Hash
# |= makes sure that the final array elements are unique
array |= make_array_from_hash_keys(array, array_value, new_prefix)
end
end
# If the value is not an array, simply add it to the main array with the
# necessary prefix
else
array << prefix + key
end
end
array
end
new_array = make_array_from_hash_keys(a, j)
puts new_array.inspect
# Gives us:
# ["name", "age", "users[]", "users[]name", "users[]colours[]", "users[]animals[]", "users[]animals[]name"]
Related
I've an array contains hashes, I want to filter few parameters from the hash and insert the filtered data in another array but am not succeed below is the sample data I've used
a = Array.new
a = [
{"name"=>"hello", "age"=>"12", "sex"=> "M", "city"=>"Chennai"},
{"name"=>"name2", "age"=>"26", "sex"=> "M", "city"=>"Banglore"}
]
line_item = Array.new
hash_data = {}
a.each do |datas|
hash_data[:name] = datas["name"]
hash_data[:age] = datas["age"]
line_item << hash_data
end
I am getting this result:
[
{:name=>"name2", :age=>"26"},
{:name=>"name2", :age=>"26"}
]
But am expecting this:
[
{:name=>"hello", :age=>"12"},
{:name=>"name2", :age=>"26"}
]
Somebody please help to sort out this, Thanks in advance
Defining the hash outside the loop means that you keep adding the same hash object again (while overwriting its previous values). Instead, create a fresh hash within the loop:
line_items = []
a.each do |datas|
hash_data = {}
hash_data[:name] = datas["name"]
hash_data[:age] = datas["age"]
line_items << hash_data
end
The code looks a bit unidiomatic. Let's refactor it.
We can set the keys right within the hash literal:
line_items = []
a.each do |datas|
hash_data = { name: datas["name"], age: datas["age"] }
line_items << hash_data
end
We can get rid of the hash_data variable:
line_items = []
a.each do |datas|
line_items << { name: datas["name"], age: datas["age"] }
end
And we can use map to directly transform the array:
line_items = a.map { |h| { name: h["name"], age: h["age"] } }
#=> [{:name=>"hello", :age=>"12"}, {:name=>"name2", :age=>"26"}]
You can get the expected result with a combination of map and slice
a = [
{"name"=>"hello", "age"=>"12", "sex"=> "M", "city"=>"Chennai"},
{"name"=>"name2", "age"=>"26", "sex"=> "M", "city"=>"Banglore"}
]
a.map{ |e| e.slice("name", "age") }
#=> [{"name"=>"hello", "age"=>"12"}, {"name"=>"name2", "age"=>"26"}]
map: Returns Array containing the values returned by block
slice: Returns Hash including only the specified keys
In your loop you are essentially populating line_item with hash_data twice. This is the same object however. You can remedy this by using .dup.
a.each do |datas|
hash_data[:name]=datas["name"]
hash_data[:age]=datas["age"]
line_item << hash_data.dup # <- here
end
irb(main):044:0> line_item
=> [{:name=>"hello", :age=>"12"}, {:name=>"name2", :age=>"26"}]
Edit: I prefer rado's suggestion of moving your definition of hash_data inside the loop over using .dup. It solves the problem more than treating the symptom.
I think a lot of people are over complicating this.
You can achieve this using the following:
a.map { |hash| hash.select { |key, _value| key == 'name' || key == 'age' } }
If you want to return an array, you should nearly always be using map, and select simply selects the key - value pairs that match the criteria.
If you're set on having symbols as the keys, you can call symbolize_keys on the result.
I'll expand the code so it's a little more readable, but the one liner above works perfectly:
a.map do |hash|
hash.select do |key, _value|
key == 'name' || key == 'age'
end
end
On the first line hash_data[:name]=datas["name"] you are setting the key of the hash. That's why when the loop iterate again, it is overriding the value and after that push the new result to the hash.
One solution with reusing this code is just to put the hash_data = {} on the first line of your loop. This way you will have a brand new hash to work with on every iteration.
Also I would recommend you to read the docs about the Hash module. You will find more useful methods there.
If you want for all keys you can do this
array = [{"name"=>"hello", "age"=>"12", "sex"=> "M", "city"=>"Chennai"}, {"name"=>"name2", "age"=>"26""sex"=> "M", "city"=>"Banglore"}]
new_array = array.map{|b| b.inject({}){|array_obj,(k,v)| array_obj[k.to_sym] = v; array_obj}}
Ref: inject
Happy Coding
I've created the following hash keys with values parsed from PDF into array:
columns = ["Sen", "P-Hire#", "Emp#", "DOH", "Last", "First"]
h = Hash[columns.map.with_index.to_h]
=> {"Sen"=>0, "P-Hire#"=>1, "Emp#"=>2, "DOH"=>3, "Last"=>4, "First"=>5}
Now I want to update the value of each key with 6 equivalent values from another parsed data array:
rows = list.text.scan(/^.+/)
row = rows[0].tr(',', '')
#data = row.split
=> ["2", "6", "239", "05/05/67", "Harp", "Erin"]
I can iterate over #data in the view and it will list each of the 6 values. When I try to do the same in the controller it sets the same value to each key:
data.each do |e|
h.update(h){|key,v1| (e) }
end
=>
{"Sen"=>"Harper", "P-Hire#"=>"Harper", "Emp#"=>"Harper", "DOH"=>"Harper", "Last"=>"Harper", "First"=>"Harper"
So it's setting the value of each key to the last value of the looped array...
I would just do:
h.keys.zip(#data).to_h
If the only purpose of h is as an interim step getting to the result, you can dispense with it and do:
columns.zip(#data).to_h
There are several ways to solve this problem but a more direct and straight forward way would be:
columns = ["Sen", "P-Hire#", "Emp#", "DOH", "Last", "First"]
...
#data = row.split
h = Hash.new
columns.each_with_index do |column, index|
h[column] = #data[index]
end
Another way:
h.each do |key, index|
h[key] = #data[index]
end
Like I said, there are several ways of solving the issue and the best is always going to depend on what you're trying to achieve.
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Array 1 = 7 elements
Array 2 = 7 elements
Hash = 7 elements
My requirement is to iterate through the each element in the hash with each element in array 1 and array 2 and come out with a new hash after applying the desired logic. The comparison is always going to be between the first element in hash against first element in array 1 and first element in array 2 and so on and so forth till I complete the list.
I am not even sure where and how to start so any help is appreciated to get me started
Is this what you are looking for?
arr1 = ['char', 'number', 'number', 'number', 'char', 'number', 'char']
arr2 = [6, '(7,0)','(15,0)','(5,0)',3,'(15,2)', 17]
h = { 'col1'=>'123456', 'col2'=>'0000111', 'col3'=>'000000002345',
'col4'=>'00023', 'col5'=>'abc', 'col6'=>'00000000000052367',
'col7'=>'0000000000321456' }
enum = arr1.zip(arr2).to_enum
#=> #<Enumerator: [["char", 6], ["number", "(7,0)"], ["number", "(15,0)"],
# ["number", "(5,0)"], ["char", 3], ["number", "(15,2)"], ["char", 17]]:each>
h.merge(h) { |*,v| [v].concat(enum.next) }
#=> {"col1"=>["123456", "char", 6], "col2"=>["0000111", "number", "(7,0)"],
# "col3"=>["000000002345", "number", "(15,0)"], "col4"=>["00023", "number", "(5,0)"],
# "col5"=>["abc", "char", 3], "col6"=>["00000000000052367", "number", "(15,2)"],
# "col7"=>["0000000000321456", "char", 17]}
This uses the form of Hash#merge that employs a block to determine the values of keys that are present in both hashes being merged, which here is all the keys of the hash.
You could use Array#zip to mix the hash and arrays :
hash = {
key1: :value1,
key2: :value2,
key3: :value3
}
array1 = %i(x1 x2 x3)
array2 = %i(y1 y2 y3)
new_hash = {}
hash.to_a.zip(array1, array2).each do |(key, value), element1, element2|
# logic with key, value, element1, and element2
# basic example :
new_hash[key] = [value, element1, element2]
end
p new_hash
# {:key1=>[:value1, :x1, :y1], :key2=>[:value2, :x2, :y2], :key3=>[:value3, :x3, :y3]}
I have included the given code:
#classes = {1=>"USA", 3=>"France", 2=>"UK", 5=>"Europe", 7=>"Delhi", 8=>"test"}
#amaze = params[:test] #I get "1,3,7"
I get this, now please guide me how to match keys with #amaze and accordingly fetch its values from #classes i.e USA, France, Delhi.
Since #amaze is just a String, lets first convert it in Array so its easy to enumerate:
#amaze = "1,3,7"
#amaze = #amaze.split(",")
# => ["1", "3", "7"]
Now, since you have all keys extract all values:
#amaze.map { |i| #classes[i.to_i] }
# => ["USA", "France", "Delhi"]
Split #amaze by , and get an array of keys, convert them into Integer, then select only those key/value pairs which key is into this array of keys. Something like this:
#classes = {1=>"USA", 3=>"France", 2=>"UK", 5=>"Europe", 7=>"Delhi", 8=>"test"}
#amaze = "1,3,7" #I get "1,3,7"
arr = #amaze.split(',').map(&:to_i)
p #classes.select{|el| arr.include? el}
Result:
#> {1=>"USA", 3=>"France", 7=>"Delhi"}
If you want values only use .values:
p #classes.select{|el| arr.include? el}.values
Result:
#> ["USA", "France", "Delhi"]
For what(seemingly) you are asking, the below line will do it:
#amaze.split(",").each { |i| p #classes[i.to_i] }
# If #amaza = "1,3,7", above line will output:
# => "USA"
# "France"
# "UK"
This should work well for you:
#classes = {1=>"USA", 3=>"France", 2=>"UK", 5=>"Europe", 7=>"Delhi", 8=>"test"}
#amaze = params[:test].split(",").map(&:to_i)
#classes.values_at(*#amaze)
#=> ["USA", "France", "Delhi"]
Hash#values_at accepts an indefinite number of keys and returns their values as an array. The * (splat) operator explodes the array so this call actually becomes #classes.values_at(1,3,7) Docs
Might also want to add a compact to the end in the event a key does not exist. e.g
#amaze = params[:test].split(",").map(&:to_i) # Asssume this returns [1,3,7,9]
#classes.values_at(*#amaze)
#=> ["USA", "France", "Delhi",nil]
#classes.values_at(*#amaze).compact
#=> ["USA", "France", "Delhi"]
I think a clearer understanding of hashes would help you out here.
A Hash is a data structure that is a list of key-value pairs. For example, the following is a Hash object of key-value pairs (your example):
#classes = {1=>"USA", 3=>"France", 2=>"UK", 5=>"Europe", 7=>"Delhi", 8=>"test"}
If you want to extract a value from #classes, you need to pass the key of the value you want. If we wanted "USA" we would pass the key of 1 to #classes. If we wanted "France", we would pass it the key of 3:
#classes[1] would return "USA" and #classes[3] would return "France".
It's not clear what data structure #amaze is according to your question, but let's say it's the string "1, 3, 7" which we can split to create an array [1, 3, 7].
You could iterate over the array to get each of the values from #classes:
#amaze.split(",").map(&:to_i).each do |key|
puts #classes[key]
end
That would print out each of the corresponding values to keys in #classes.
I have this code here and it works but there has to be a better way.....i need two arrays that look like this
[
{
"Vector Arena - Auckland Central, New Zealand" => {
"2010-10-10" => [
"Enter Sandman",
"Unforgiven",
"And justice for all"
]
}
},
{
"Brisbane Entertainment Centre - Brisbane Qld, Austr..." => {
"2010-10-11" => [
"Enter Sandman"
]
}
}
]
one for the past and one for the upcoming...the problem i have is i am repeating myself and though it works i want to clean it up ...here is my data
..
Try this:
h = Hash.new {|h1, k1| h1[k1] = Hash.new{|h2, k2| h2[k2] = []}}
result, today = [ h, h.dup], Date.today
Request.find_all_by_artist("Metallica",
:select => "DISTINCT venue, showdate, LOWER(song) AS song"
).each do |req|
idx = req.showdate < today ? 0 : 1
result[idx][req.venue][req.showdate] << req.song.titlecase
end
Note 1
In the first line I am initializing an hash of hashes. The outer hash creates the inner hash when a non existent key is accessed. An excerpt from Ruby Hash documentation:
If this hash is subsequently accessed by a key that doesn‘t correspond to a hash
entry, the block will be called with the hash object and the key, and should
return the default value. It is the block‘s responsibility to store the value in
the hash if required.
The inner hash creates and empty array when the non existent date is accessed.
E.g: Construct an hash containing of content as values and date as keys:
Without a default block:
h = {}
list.each do |data|
h[data.date] = [] unless h[data.date]
h[data.date] << data.content
end
With a default block
h = Hash.new{|h, k| h[k] = []}
list.each do |data|
h[data.date] << data.content
end
Second line simply creates an array with two items to hold the past and future data. Since both past and the present stores the data as Hash of Hash of Array, I simply duplicate the value.
Second line can also be written as
result = [ h, h.dup]
today = Date.today