I have a hash of people keyed by job and sorted by salary:
person = Struct.new(:salary)
people = {
:butchers => [
person.new(10),
person.new(6),
person.new(4)
],
:bakers => [
person.new(16),
person.new(8),
person.new(7)
],
:candlestick_makers => [
person.new(25),
person.new(21),
person.new(18)
]
}
I want to remove the last x people of each job from their respective array and do something:
def this_example_method
people.each do |job, people|
people.pop(number_for(job)).each do |person|
#do something
end
end
end
the 'do something' works okay, but pop removal doesn't. After running this_example_method, the people hash should look this, but at the moment it's not changing:
people = {
butchers = [
<butcher_1 salary:10>
<butcher_2 salary:6>
],
bakers = [
<baker_1 salary:16>
<baker_2 salary:8>
],
candlestick_makers = [
<candlestick_maker_1 salary:25>
<candlestick_maker_2 salary:21>
]
}
Hash has a shift method that returns the first item and removes it from the hash. If the order matters you could perhaps try to sort it reversed when the hash is created.
Just do as below :
def this_example_method
people.each do |job, persons|
persons.tap { |ob| ob.pop(x) }.each do |person|
#do something
end
end
end
Example :
hash = { :a => [1,2,3], :b => [3,5,7] }
hash.each do |k,v|
v.tap(&:pop).each { |i| # working wit i }
end
hash # => {:a=>[1, 2], :b=>[3, 5]}
Related
I have:
people=["Bob","Fred","Sam"]
holidays = Hash.new
people.each do |person|
a=Array.new
holidays[person]=a
end
gifts = Hash.new
people.each do |person|
a=Array.new
gifts[person]=a
end
Feels clunky. I can't seem to figure a more streamline way with an initialization block or somesuch thing. Is there an idiomatic approach here?
Ideally, I'd like to keep an array like:
lists["holidays","gifts",...]
... and itterate through it to initialize each element in the lists array.
people = %w|Bob Fred Sam|
data = %w|holidays gifts|
result = data.zip(data.map { people.zip(people.map { [] }).to_h }).to_h
result['holidays']['Bob'] << Date.today
#⇒ {
# "holidays" => {
# "Bob" => [
# [0] #<Date: 2016-11-04 ((2457697j,0s,0n),+0s,2299161j)>
# ],
# "Fred" => [],
# "Sam" => []
# },
# "gifts" => {
# "Bob" => [],
# "Fred" => [],
# "Sam" => []
# }
# }
More sophisticated example would be:
result = data.map do |d|
[d, Hash.new { |h, k| h[k] = [] if people.include?(k) }]
end.to_h
The latter produces the “lazy initialized nested hashes.” It uses the Hash#new with a block constructor for nested hashes.
Play with it to see how it works.
A common way of doing that would be to use Enumerable#each_with_objrect.
holidays = people.each_with_object({}) { |p,h| h[p] = [] }
#=> {"Bob"=>[], "Fred"=>[], "Sam"=>[]}
gifts is the same.
If you only want a number of such hashes then, the following should suffice:
count_of_hashes = 4 // lists.count; 4 is chosen randomly by throwing a fair die
people = ["Bob", "Fred", "Sam"]
lists = count_of_hashes.times.map do
people.map {|person| [person, []]}.to_h
end
This code also ensures the arrays and the hashes all occupy their own memory. As can be verified by the following code:
holidays, gifts, *rest = lists
holidays["Bob"] << "Rome"
And checking the values of all the other hashes:
lists
=> [
{"Bob"=>["Rome"], "Fred"=>[], "Sam"=>[]},
{"Bob"=>[], "Fred"=>[], "Sam"=>[]},
{"Bob"=>[], "Fred"=>[], "Sam"=>[]},
{"Bob"=>[], "Fred"=>[], "Sam"=>[]}
]
I am using the mysql2 gem to connect to my database and pull out data. It's a simple query
statement = #db.prepare('SELECT * FROM my_table')
#result = statement.execute
This returns a Mysql2::Result object, I know to iterate through I do this
#result.each do |r|
puts r
end
Which will give back in my case
[
{"id"=>1,
"name"=>"Standard",
"label"=>"Standard",
"amount"=>100,
"created_at"=>2010-11-17 11:50:38 +0000,
"updated_at"=>2010-11-17 11:50:38 +0000,
"status"=>"active",
"dataprofileid"=>"0",
"groupid"=>1},
{"id"=>2,
"name"=>"Director Register",
"label"=>"Director Register",
"amount"=>150,
"created_at"=>2010-11-17 11:51:11 +0000,
"updated_at"=>2010-11-17 11:51:11 +0000,
"status"=>"active",
"dataprofileid"=>"18",
"groupid"=>0}
]
From this I want to create a Hash that looks like
{ "Standard"=> { "id"=>1, "dataprofileid"=> 0 }}
So for each record use the name as the key, and then have further key/values inside. At the moment I have created a regular Hash with name as the key and the id as the value but am not sure on how to get to the next stage
#credit_ids = []
#credit_names = []
#credit_dataprof = []
#result.each do |r|
#credit_names << r['name']
#credit_ids << r['id']
#credit_dataprof << r['dataprofileid']
end
#credit_hash = Hash[#credit_names.zip #credit_ids]
map() your array to the hashs that you actually want as values.
Use Enumerable#group_by.
This will allow you to get all the hashs by name, with the full hash following.
or I didn't get your question. :)
I come across another answer on SO and come up with this which works, hopefully it helps someone else
h = Hash.new{|hsh, key| hsh[key] = {} }
#result.each do |r|
h[r['name']].store 'id', r['id']
h[r['name']].store 'dataprofileid', r['dataprofileid']
end
This then returns
{
"Standard"=> { "id" => 1, "dataprofileid" => "0" },
"CCJ" => { "id" => 5, "dataprofileid" => "20" }
# Many more ommitted but you get the idea
}
Open for suggestions mind to improve this
The naive:
#result.map{
|h| {h["name"] => {"id" => h["id"], "dataprorileid" => h["dataprofileid"]}}
}
will give you:
[
{"Standard"=>{"id"=>1, "dataprorileid"=>"0"}},
{"Director Register"=>{"id"=>2, "dataprorileid"=>"18"}}
]
But if you want to respect the original structure (with the key-value pairs other than "name" retained), then:
#result.map{|h| k = h.dup.delete("name"); {k => h}}
will give you:
[
{"Standard"=>{"id"=>1, "name"=>"Standard", "label"=>"Standard", "amount"=>100, "created_at"=>2016-01-14 20:47:04 +0900, "updated_at"=>2016-01-14 20:47:04 +0900, "status"=>"active", "dataprofileid"=>"0", "groupid"=>1}},
{"Director Register"=>{"id"=>2, "name"=>"Director Register", "label"=>"Director Register", "amount"=>150, "created_at"=>2016-01-14 20:47:04 +0900, "updated_at"=>2016-01-14 20:47:04 +0900, "status"=>"active", "dataprofileid"=>"18", "groupid"=>0}}
]
#credit_ids = []
#credit_names = []
#credit_dataprof = []
#credit_hash = Hash.new()
#result.each do |r|
#credit_names = r['name']
#credit_ids = r['id']
#credit_dataprof = r['dataprofileid']
#credit_hash = #credit_hash.merge({#credit_names => {"id" => #credit_ids, "dataprofileid" => #credit_dataprof}})
end
puts #credit_hash
produces:
{"Standard"=>{"id"=>1, "dataprofileid"=>"0"}, "Director Register"=>{"id"=>2, "dataprofileid"=>"18"}}
I have a Hash that looks like this:
{
:a => "700",
:b => "600",
:c => "500",
:d => "400",
:e => "300",
:f => {
:g => "200",
:h => [
"test"
]
}
}
my goal is to iterate over this hash and return a copy that have all the values wrapped in a lambda, similar to this: https://github.com/thoughtbot/paperclip/blob/dca87ec5d8038b2d436a75ad6119c8eb67b73e70/spec/paperclip/style_spec.rb#L44
I went with each_with_object({}) but best I can do is to wrap only the first level, so I tried to check when I meet another Hash in the cycle (:f in this case, only it's key's values should be a lambda unless they are a hash as well) and treat it, but it's becoming quite troublesome.
def hash_values_to_lambda(old_hash)
{}.tap do |new_hash|
old_hash.each do |key, value|
new_hash[key] =
if value.is_a?(Hash)
hash_values_to_lambda(value)
else
lambda { value } # or -> { value } with new syntax
end
end
end
end
If you want, you can go with each_with_object instead of tap:
old_hash.each_with_object({}) do |(key, value), new_hash|
# everything else remains the same
end
I have a db query which returns results like:
db_result.each {|row| puts row}
{"IP"=>"1.2.3.4","Field1"=>"abc","Field2"=>"123"}
{"IP"=>"1.2.3.4","Field1"=>"abc","Field2"=>"234"}
{"IP"=>"1.2.3.4","Field1"=>"bcd","Field2"=>"345"}
{"IP"=>"3.4.5.6","Field1"=>"bcd","Field2"=>"456"}
{"IP"=>"3.4.5.6","Field1"=>"bcd","Field2"=>"567"}
And want to put it into a hash like:
{
"1.2.3.4" => {
"abc" => ["123", "234"],
"bcd" => "345"
},
"3.4.5.6" => {
"bcd" => ["456", "567"]
}
}
What I am currently doing is:
result_hash = Hash.new { |h, k| h[k] = {} }
db_result.each do |row|
result_hash[row["IP"]] = Hash.new { |h, k| h[k] = [] } unless result_hash.has_key? row["IP"]
result_hash[row["IP"]][row["Field1"]] << row["Field2"]
end
Which works, however was wondering if there is a neater way.
Consider this a peer-review. As a recommendation for processing and maintenance...
I'd recommend the data structure you want be a little more consistent.
Instead of:
{
"1.2.3.4" => {
"abc" => ["123", "234"],
"bcd" => "345"
},
"3.4.5.6" => {
"bcd" => ["456", "567"]
}
}
I'd recommend:
{
"1.2.3.4" => {
"abc" => ["123", "234"],
"bcd" => ["345"]
},
"3.4.5.6" => {
"abc" => [],
"bcd" => ["456", "567"]
}
}
Keep the same keys in each sub-hash, and make the values all be arrays. The code for processing that overall hash will be more straightforward and easy to follow.
I agree with Michael, there is nothing wrong with your method. The intent behind the code can be easily seen.
If you want to get fancy, here's one (of many) ways to do it:
x = [
{"IP"=>"1.2.3.4","Field1"=>"abc","Field2"=>"123"},
{"IP"=>"1.2.3.4","Field1"=>"abc","Field2"=>"234"},
{"IP"=>"1.2.3.4","Field1"=>"bcd","Field2"=>"345"},
{"IP"=>"3.4.5.6","Field1"=>"bcd","Field2"=>"456"},
{"IP"=>"3.4.5.6","Field1"=>"bcd","Field2"=>"567"}
]
y = x.inject({}) do |result, row|
new_row = result[row["IP"]] ||= {}
(new_row[row["Field1"]] ||= []) << row["Field2"]
result
end
I think this should yield the same time complexity as your method.
I have a Ruby hash which looks like:
{ "id" => "123", "name" => "test" }
I would like to convert it to:
{ :id => "123", :name => "test" }
hash = {"apple" => "banana", "coconut" => "domino"}
Hash[hash.map{ |k, v| [k.to_sym, v] }]
#=> {:apple=>"banana", :coconut=>"domino"}
#mu is too short: Didn't see word "recursive", but if you insist (along with protection against non-existent to_sym, just want to remind that in Ruby 1.8 1.to_sym == nil, so playing with some key types can be misleading):
hash = {"a" => {"b" => "c"}, "d" => "e", Object.new => "g"}
s2s =
lambda do |h|
Hash === h ?
Hash[
h.map do |k, v|
[k.respond_to?(:to_sym) ? k.to_sym : k, s2s[v]]
end
] : h
end
s2s[hash] #=> {:d=>"e", #<Object:0x100396ee8>=>"g", :a=>{:b=>"c"}}
If you happen to be in Rails then you'll have symbolize_keys:
Return a new hash with all keys converted to symbols, as long as they respond to to_sym.
and symbolize_keys! which does the same but operates in-place. So, if you're in Rails, you could:
hash.symbolize_keys!
If you want to recursively symbolize inner hashes then I think you'd have to do it yourself but with something like this:
def symbolize_keys_deep!(h)
h.keys.each do |k|
ks = k.to_sym
h[ks] = h.delete k
symbolize_keys_deep! h[ks] if h[ks].kind_of? Hash
end
end
You might want to play with the kind_of? Hash to match your specific circumstances; using respond_to? :keys might make more sense. And if you want to allow for keys that don't understand to_sym, then:
def symbolize_keys_deep!(h)
h.keys.each do |k|
ks = k.respond_to?(:to_sym) ? k.to_sym : k
h[ks] = h.delete k # Preserve order even when k == ks
symbolize_keys_deep! h[ks] if h[ks].kind_of? Hash
end
end
Note that h[ks] = h.delete k doesn't change the content of the Hash when k == ks but it will preserve the order when you're using Ruby 1.9+. You could also use the [(key.to_sym rescue key) || key] approach that Rails uses in their symbolize_keys! but I think that's an abuse of the exception handling system.
The second symbolize_keys_deep! turns this:
{ 'a' => 'b', 'c' => { 'd' => { 'e' => 'f' }, 'g' => 'h' }, ['i'] => 'j' }
into this:
{ :a => 'b', :c => { :d => { :e => 'f' }, :g => 'h' }, ['i'] => 'j' }
You could monkey patch either version of symbolize_keys_deep! into Hash if you really wanted to but I generally stay away from monkey patching unless I have very good reasons to do it.
If you are using Rails >= 4 you can use:
hash.deep_symbolize_keys
hash.deep_symbolize_keys!
or
hash.deep_stringify_keys
hash.deep_stringify_keys!
see http://apidock.com/rails/v4.2.1/Hash/deep_symbolize_keys
Just in case you are parsing JSON, from the JSON docs you can add the option to symbolize the keys upon parsing:
hash = JSON.parse(json_data, symbolize_names: true)
Victor Moroz provided a lovely answer for the simple recursive case, but it won't process hashes that are nested within nested arrays:
hash = { "a" => [{ "b" => "c" }] }
s2s[hash] #=> {:a=>[{"b"=>"c"}]}
If you need to support hashes within arrays within hashes, you'll want something more like this:
def recursive_symbolize_keys(h)
case h
when Hash
Hash[
h.map do |k, v|
[ k.respond_to?(:to_sym) ? k.to_sym : k, recursive_symbolize_keys(v) ]
end
]
when Enumerable
h.map { |v| recursive_symbolize_keys(v) }
else
h
end
end
Try this:
hash = {"apple" => "banana", "coconut" => "domino"}
# => {"apple"=>"banana", "coconut"=>"domino"}
hash.tap do |h|
h.keys.each { |k| h[k.to_sym] = h.delete(k) }
end
# => {:apple=>"banana", :coconut=>"domino"}
This iterates over the keys, and for each one, it deletes the stringified key and assigns its value to the symbolized key.
If you're using Rails (or just Active Support):
{ "id" => "123", "name" => "test" }.symbolize_keys
Starting with Ruby 2.5 you can use the transform_key method.
So in your case it would be:
h = { "id" => "123", "name" => "test" }
h.transform_keys!(&:to_sym) #=> {:id=>"123", :name=>"test"}
Note: the same methods are also available on Ruby on Rails.
Here's a Ruby one-liner that is faster than the chosen answer:
hash = {"apple" => "banana", "coconut" => "domino"}
#=> {"apple"=>"banana", "coconut"=>"domino"}
hash.inject({}){|h,(k,v)| h[k.intern] = v; h}
#=> {:apple=>"banana", :coconut=>"domino"}
Benchmark results:
n = 100000
Benchmark.bm do |bm|
bm.report { n.times { hash.inject({}){|h,(k,v)| h[k.intern] = v; h} } }
bm.report { n.times { Hash[hash.map{ |k, v| [k.to_sym, v] }] } }
end
# => user system total real
# => 0.100000 0.000000 0.100000 ( 0.107940)
# => 0.120000 0.010000 0.130000 ( 0.137966)
I'm partial to:
irb
ruby-1.9.2-p290 :001 > hash = {"apple" => "banana", "coconut" => "domino"}
{
"apple" => "banana",
"coconut" => "domino"
}
ruby-1.9.2-p290 :002 > hash.inject({}){ |h, (n,v)| h[n.to_sym] = v; h }
{
:apple => "banana",
:coconut => "domino"
}
This works because we're iterating over the hash and building a new one on the fly. It isn't recursive, but you could figure that out from looking at some of the other answers.
hash.inject({}){ |h, (n,v)| h[n.to_sym] = v; h }
You can also extend core Hash ruby class placing a /lib/hash.rb file :
class Hash
def symbolize_keys_deep!
new_hash = {}
keys.each do |k|
ks = k.respond_to?(:to_sym) ? k.to_sym : k
if values_at(k).first.kind_of? Hash or values_at(k).first.kind_of? Array
new_hash[ks] = values_at(k).first.send(:symbolize_keys_deep!)
else
new_hash[ks] = values_at(k).first
end
end
new_hash
end
end
If you want to make sure keys of any hash wrapped into arrays inside your parent hash are symbolized, you need to extend also array class creating a "array.rb" file with that code :
class Array
def symbolize_keys_deep!
new_ar = []
self.each do |value|
new_value = value
if value.is_a? Hash or value.is_a? Array
new_value = value.symbolize_keys_deep!
end
new_ar << new_value
end
new_ar
end
end
This allows to call "symbolize_keys_deep!" on any hash variable like this :
myhash.symbolize_keys_deep!
def symbolize_keys(hash)
new={}
hash.map do |key,value|
if value.is_a?(Hash)
value = symbolize_keys(value)
end
new[key.to_sym]=value
end
return new
end
puts symbolize_keys("c"=>{"a"=>2,"k"=>{"e"=>9}})
#{:c=>{:a=>2, :k=>{:e=>9}}}
Here's my two cents,
my version of symbolize_keys_deep! uses the original symbolize_keys! provided by rails and just makes a simple recursive call to Symbolize sub hashes.
def symbolize_keys_deep!(h)
h.symbolize_keys!
h.each do |k, v|
symbolize_keys_deep!(v) if v.is_a? Hash
end
end
Facets' Hash#rekey is also a worth mentioning.
Sample:
require 'facets/hash/rekey'
{ "id" => "123", "name" => "test" }.deep_rekey
=> {:id=>"123", :name=>"test"}
There is also a recursive version:
require 'facets/hash/deep_rekey'
{ "id" => "123", "name" => {"first" => "John", "last" => "Doe" } }.deep_rekey
=> {:id=>"123", :name=>{:first=>"John", :last=>"Doe"}}
Here's a little recursive function to do a deep symbolization of the keys:
def symbolize_keys(hash)
Hash[hash.map{|k,v| v.is_a?(Hash) ? [k.to_sym, symbolize_keys(v)] : [k.to_sym, v] }]
end