I have an array of hashes (#1) that looks like this:
data = [{"username"=>"Luck", "mail"=>"root#localhost.net", "active"=>0}]
that I am trying to compare with following array of hashes (#2):
test = [{"username"=>"Luck", "mail"=>"root#localhost.net", "active"=>"0"}]
where #1 I obtained from database by mysql2 (what actually is in the database)
and #2 from my cucumber scenario (what I minimally expect ot be there).
By definition #2 must be a subset of #1 so I follow with this code:
data = data.to_set
test = test.to_set
assert test.subset?(data)
The problem is in data array the value of active is NOT a string. In case of data it is Fixnum, and in case of test, it is String.
I need a solution that will work even for more than one hash in the array. (As the database can return more than one row of results) That is why I convert to sets and use subset?
From other questions I got:
data.each do |obj|
obj.map do |k, v|
{k => v.to_s}
end
end
However it does not work for me. Any ideas?
Assumptions you can make:
All the keys in data will always be Strings.
All the keys in test will always be Strings. And always be the identical to data.
All the values in test will always be Strings.
Here are a couple of approaches that should do it, assuming I understand the question correctly.
#1: convert the hash values to strings
def stringify_hash_values(h)
h.each_with_object({}) { |(k,v),h| h[k] = v.to_s }
end
def sorta_subset?(data,test)
(test.map { |h| stringify_hash_values(data) } -
data.map { |h| stringify_hash_values(data) }).empty?
end
data = [{"username"=>"Luck", "mail"=>"root#localhost.net", "active"=>0}]
test = [{"username"=>"Luck", "mail"=>"root#localhost.net", "active"=>"0"}]
sorta_subset?(data,test) #=> true
#2 see if keys are the same and values converted to strings are equal
require 'set'
def hashes_sorta_equal?(h,g)
hk = h.keys
(hk.to_set == g.keys.to_set) &&
(h.values_at(*hk).map(&:to_s) == g.values_at(*hk).map(&:to_s))
end
def sorta_subset?(data,test)
test.all? { |h| data.any? { |g| hashes_sorta_equal?(g,h) } }
end
sorta_subset?(data,test) #=> true
Don't ask me why it works, but I found A solution:
data.map! do |obj|
obj.each do |k, v|
obj[k] = "#{v}"
end
end
I think it has something to do with what functions on arrays and hashes change the object itself and not create a changed copy of the object.
Related
I have two hashes like this:
hash1 = Hash.new
hash1["part1"] = "test1"
hash1["part2"] = "test2"
hash1["part3"] = "test3"
hash2 = Hash.new
hash2["part1"] = "test1"
hash2["part2"] = "test2"
hash2["part3"] = "test4"
Expected output: part3
Basically, I want to iterate both of the hashes and print out "part3" because the value for "part3" is different in the hash. I can guarantee that the keys for both hashes will be the same, the values might be different. I want to print out the keys when their values are different?
I have tried iterating both hashes at once and comparing values but does not seem to give the right solution.
The cool thing about Ruby is that it is so high level that it is often basically English:
Print keys from the first hash if the values in the two hashes are different:
hash1.keys.each { |key| puts key if hash1[key] != hash2[key] }
Select the first hash keys that have different values in the two hashes and print each of them:
hash1.keys.select { |key| hash1[key] != hash2[key] }.each { |key| puts key }
Edit: I'll leave this should it be of interest, but #ndn's solution is certainly better.
p hash1.merge(hash2) { |_,v1,v2| v1==v2 }.reject { |_,v| v }.keys
# ["part3"]
hash1["part1"] = "test99"
p hash1.merge(hash2) { |_,v1,v2| v1==v2 }.reject { |_,v| v }.keys
# ["part1", "part3"]
This uses the form of Hash#merge that employs a block (here { |_,v1,v2| v1==v2 }) to determine the values of keys that are present in both hashes being merged. See the doc for an explanation of the three block variables, _, v1 and v2. The first block variable equals the common key. I've used the local variable _ for that, as is customary when the variable is not used in the block calculation.
The steps (for the original hash1):
g = hash1.merge(hash2) { |_,v1,v2| v1==v2 }
#=> {"part1"=>true, "part2"=>true, "part3"=>false}
h = g.reject { |_,v| v }
#=> {"part3"=>false}
h.keys
#=> ["part3"]
The obvious way is that of ndn, here a solution without blocks by converting to arrays, joining them and subtracting the elements that are the same, followed by converting back to hash and asking for the keys.
Next time it would be better to include what you tried so far.
((hash1.to_a + hash2.to_a) - (hash1.to_a & hash2.to_a)).to_h.keys
# ["part3"]
Part of class KeyServer
#generated_keys = Hash.new
def generate_key
key = SecureRandom.urlsafe_base64
while(purged_keys.include?(key))
key = SecureRandom.urlsafe_base64
end
#add new key to hashes that maintain records
#generated_keys.merge!({key => Time.now})
#all_keys.merge!(#generated_keys) { |key, v1, v2| v1 }
return key
end
And I use the generated keys here: (I need a random pair to be selected and allotted to user)
def get_available_key
if(generated_keys.empty?)
return "404. No keys available"
else
new_key = #generated_keys.to_a.sample(1)
#generated_keys.delete(new_key[0][0].to_s)
#blocked_keys.merge!({new_key[0][0].to_s => Time.now})
end
end
This is how I use it in Sinatra
api = KeyServer.new
get '/block_key' do
api.get_available_key
end
I tried the solution mentioned in this question but when I run this as part of my Sinatra server I obtain an Internal Server Error: No implicit conversion from Array to String
How do I make this work? Any other method to obtain a random pair from a Hash would be welcome.
To get a random element from a Hash to return as a Hash you could simply patch Hash to do this like
class Hash
def sample(n)
Hash[to_a.sample(n)]
end
end
Then call like
h = {a: 1, b: 2, c: 3}
h.sample(1)
#=> {b: 2}
h.sample(2)
#=> {:b=>2, :a=>1}
Note: I used Hash::[] for compatibility purposes in Ruby 2.X you could use to_h instead.
Other than that I think there might be a few more issues with your code and it's return values.
If I were to refactor your code the sample code above would not be needed I would instead go with something like it would be something like
def get_available_key
if(generated_keys.empty?)
{"error" => "404. No keys available"}
else
new_key = #generated_keys.keys.sample(1)
#generated_keys.delete(new_key)
#blocked_keys.merge!({new_key => Time.now})[new_key]
end
end
This way it will always respond with a Hash object for handling purposes and it need not worry about multidimensional arrays at all.
I would also change the initial code to be more like this
def create_new_key
key = SecureRandom.urlsafe_base64
purged_keys.include?(key) ? create_new_key : key
end
def generate_key
key = create_new_key
#add new key to hashes that maintain records
#generated_keys.merge!({key => Time.now})
#all_keys.merge!(#generated_keys) { |key, v1, v2| v1 }
key
end
def add_to_key_chain(length)
#generated_keys ||= {}
length.times do
create_new_key
end
end
Although I don't know what the purged_keys method looks like.
hash.to_a.sample evaluates to a two-element array where the first element is some key and the second is the corresponding value.
When you call delete you should be using hash.delete(new_key[0]) instead of hash.delete(new_key[0][0].to_s).
I have a terribly nested Json response.
[[{:test=>[{:id=>1, :b=>{id: '2'}}]}]]
There's more arrays than that but you get the idea.
Is there a way to recursively search through and find all the items that have a key I need?
I tried using this function extract_list() but it doesn't handle arrays well.
def nested_find(obj, needed_keys)
return {} unless obj.is_a?(Array) || obj.is_a?(Hash)
obj.inject({}) do |hash, val|
if val.is_a?(Hash) && (tmp = needed_keys & val.keys).length > 0
tmp.each { |key| hash[key] = val[key] }
elsif val.is_a?(Array)
hash.merge!(obj.map { |v| nested_find(v, needed_keys) }.reduce(:merge))
end
hash
end
end
Example
needed_keys = [:id, :another_key]
nested_find([ ['test', [{id:1}], [[another_key: 5]]]], needed_keys)
# {:id=>1, :another_key=>5}
The following is not what I'd suggest, but just to give a brief alternative to the other solutions provided:
2.1.1 :001 > obj = [[{:test=>[{:id=>1, :b=>{id: '2'}}]}]]
=> [[{:test=>[{:id=>1, :b=>{:id=>"2"}}]}]]
2.1.1 :002 > key = :id
=> :id
2.1.1 :003 > obj.inspect.scan(/#{key.inspect}=>([^,}]*)[,}]/).flatten.map {|s| eval s}
=> [1, "2"]
Note: use of eval here is just for an example. It would fail/produce incorrect results on anything whose inspect value was not eval-able back to the same instance, and it can execute malicious code:
You'll need to write your own recursive handler. Assuming that you've already converted your JSON to a Ruby data structure (via JSON.load or whatnot):
def deep_find_value_with_key(data, desired_key)
case data
when Array
data.each do |value|
if found = deep_find_value_with_key value, desired_key
return found
end
end
when Hash
if data.key?(desired_key)
data[desired_key]
else
data.each do |key, val|
if found = deep_find_value_with_key(val, desired_key)
return found
end
end
end
end
return nil
end
The general idea is that given a data structure, you check it for the key (if it's a hash) and return the matching value if found. Otherwise, you iterate it (if it's an Array or Hash) and perform the same check on each of it's children.
This will find the value for the first occurrence of the given key, or nil if the key doesn't exist in the tree. If you need to find all instances then it's slightly different - you basically need to pass an array that will accumulate the values:
def deep_find_value_with_key(data, desired_key, hits = [])
case data
when Array
data.each do |value|
deep_find_value_with_key value, desired_key, hits
end
when Hash
if data.key?(desired_key)
hits << data[desired_key]
else
data.each do |key, val|
deep_find_value_with_key(val, desired_key)
end
end
end
return hits
end
I am wondering how one would search through an array of hashes and return a value based on a search string. For example, #contacts contains the hash elements: :full_name, :city, and :email. The variable #contacts (I guess it would be an array) contains three entries (perhaps rows). Below is the code I have so far to conduct a search based on :city value. However it's not working. Can anyone give me an idea what's going on?
def search string
#contacts.map {|hash| hash[:city] == string}
end
You should use select instead of map:
def search string
#contacts.select { |hash| hash[:city] == string }
end
In your code you tried to map (or transform) your array using a block, which yields boolean values. map takes a block and invokes the block for each element of self, constructing a new array containing elements returned by the block. As the result, you got an array of booleans.
select works similar. It takes a block and iterates over the array as well, but instead of transforming the source array it returns an array containing elements for which the block returns true. So it's a selection (or filtering) method.
In order to understand the difference between these two methods it's useful to see their example definitions:
class Array
def my_map
[].tap do |result|
self.each do |item|
result << (yield item)
end
end
end
def my_select
[].tap do |result|
self.each do |item|
result << item if yield item
end
end
end
end
Example usage:
irb(main):007:0> [1,2,3].my_map { |x| x + 1 }
[2, 3, 4]
irb(main):008:0> [1,2,3].my_select { |x| x % 2 == 1 }
[1, 3]
irb(main):009:0>
You can try this:
def search string
#contacts.select{|hash| h[:city].eql?(string) }
end
This will return an array of hashes which matches string.
I was wondering if there is a more elegant way of writing the following lines:
section_event_hash = []
sections.each do |s|
section_event_hash << { s => s.find_all_events }
end
I want to create a hash whose keys are the elements of sections, and the values are arrays of elements returned by the find_all_events method.
If you want section_event_hash to really be a Hash rather than an Array, then you could use each_with_object:
section_event_hash = sections.each_with_object({}) { |s, h| h[s] = s.find_all_events }
You could use map to build an array of arrays and then feed that to Hash[]:
section_event_hash = Hash[sections.map { |s| [s, s.find_all_events] }]
The code you posted isn't quite doing what you said you want. Let's take a closer look at it by testing like so:
sections = ["ab", "12"]
section_event_hash = []
sections.each do |s|
section_event_hash << { s => s.split("") }
end
puts section_event_hash.inspect
Gives:
[{"ab"=>["a", "b"]}, {"12"=>["1", "2"]}]
So you've actually created an array of hashes, where each hash contains one key-value pair.
The following code produces one hash with multiple elements. Notice how an empty hash is created with {} instead of []. Curly braces are the symbol for a hash, while the square brackets refer to a particular key.
section_event_hash = {}
sections.each do |s|
section_event_hash[s] = s.split("")
end
puts section_event_hash.inspect
=> {"ab"=>["a", "b"], "12"=>["1", "2"]}
As for a "more elegant" way of doing it, well that depends on your definition. As the other answers here demonstrate, there is usually more than one way to do something in ruby. seph's produces the same data structure as your original code, while mu's produces the hash you describe. Personally, I'd just aim for code that is easy to read, understand, and maintain.
array_of_section_event_hashes = sections.map do |s|
{s => s.find_all_events}
end