I have a Rails nested hash as follow:
class = [{"tutor" => {"id" => "Me"}}, {"tutor" => {}}]
I would like to extract id list, but the nested hash can be nil:
tutor_ids = class.map {|c| c['tutor']['id'].to_i }
In case the nested hash is nil, I'll get error.
How do I go about this?
First of all I think you were probably thinking of an array of hashes like so (given the same key was used multiple times:
klass = [{"tutor" => {"id" => "Me"}},{"tutor" => {}}]
Then you could map the tutor IDs with:
tutor_ids = klass.map {|k| k['tutor'] && k['tutor']['id'] }.compact
which would result in
=> ["Me"]
Compact will throw out all the nil values encountered afterwards.
id = class['tutor'] ? class['tutor']['id'] : nil
Related
I receive a param and want it to be either a string like this :
"abc,efg"
or an Array like this
["abc","efg"]
In the first case I want to convert it into an Array, what would be the good way ?
Here is what I thought
if params[:ids] && params[:ids].is_a? Array
ids = params[:ids]
else if params[:ids]
ids = params[:ids].split(",")
I'd use a ternary for this to keep it simple and on one line:
ids = params[:ids].is_a?(String) ? params[:ids].split(',') : params[:ids]
I've reversed the order so you don't get an undefined method error if you try calling split on nil should params[:ids] be missing.
Array.wrap(params[:ids]).map{|x| x.split(',')}.flatten
Apologies for piling on. But I thought I would offer a slight tweak to the answer proposed by SickLickWill (which doesn't quite handle the Array case correctly):
ids = params[:id].split(',').flatten
This will handle the String case just fine:
:001 > params = {id: "abc,efg"}
:002 > ids = params[:id].split(',').flatten
=> ["abc", "efg"]
As well as the Array case:
:003 > params = {id: ["abc","efg"]}
:004 > ids = params[:id].split(',').flatten
=> ["abc", "efg"]
If there's any chance the id param will be nil, then this barfs:
:005 > params = {}
=> {}
:006 > ids = params[:id].split(',').flatten
NoMethodError: undefined method `split' for nil:NilClass
So, you could put in a conditional test:
:007 > ids = params[:id].split(',').flatten if params[:id]
=> nil
Or, use try:
:008 > ids = params[:id].try(:split, ',').try(:flatten)
=> nil
You miss end tag and you have wrong else if and you can delete the check of params[:ids] because if :ids key do not exist is_a? return NilClass
I think you can do this
ids = if params[:ids].is_a? Array
params[:ids]
elsif params[:ids]
params[:ids].split(",")
end
I think the shortest way would be to use .try. It saves you from writing out an if-then-else.
params_id = params[:id].try(:split, ',')
I am creating an array of fields
def create_fields fields
fields_list = []
fields.each do |field|
# puts "adding_field to array: #{field}"
field_def = { field: field, data: { type: 'Text', description: '' } }
fields_list.push field_def
end
fields_list
end
The fields_list is being set to a jsonb field.
Lets say I pass in
create_fields ['Ford', 'BMW', 'Fiat']
Json result is an array:
{"field"=>"Ford", "data"=>{"type"=>"Text", "description"=>""}}
{"field"=>"BMW", "data"=>{"type"=>"Text", "description"=>""}}
{"field"=>"Fiat", "data"=>{"type"=>"Text", "description"=>""}}
How can I access the 'Ford' from the json array? Am i creating the array incorrectly? Is there a better way to create this array so I can access the field i want?
This assertion passes assert_equal(3, fields.count)
However i want to get 'Ford' and check it's properties, e.g. type = 'Text', type could equal 'Number' or whatever.
The result of your create_fields method with the specified parameters is the following:
[
{:field=>"Ford", :data=>{:type=>"Text", :description=>""}},
{:field=>"BMW", :data=>{:type=>"Text", :description=>""}},
{:field=>"Fiat", :data=>{:type=>"Text", :description=>""}}
]
It means that if you want to access the line belonging to "Ford", you need to search for it like:
2.3.1 :019 > arr.select{|e| e[:field] == "Ford" }
=> [{:field=>"Ford", :data=>{:type=>"Text", :description=>""}}]
2.3.1 :020 > arr.select{|e| e[:field] == "Ford" }[0][:data][:type]
=> "Text"
This is not optimal, because you need to search an array O(n) instead of using the pros of a hash. If there are e.g.: 2 "Ford" lines, you'll get an array which contains 2 elements, harder to handle collisions in field value.
It would be better if you created the array like:
def create_fields fields
fields_list = []
fields.each do |field|
# puts "adding_field to array: #{field}"
field_def = [field, { type: 'Text', description: '' } ]
fields_list.push field_def
end
Hash[fields_list]
end
If you choose this version, you can access the members like:
2.3.1 :072 > arr = create_fields ['Ford', 'BMW', 'Fiat']
=> {"Ford"=>{:type=>"Text", :description=>""}, "BMW"=>{:type=>"Text", :description=>""}, "Fiat"=>{:type=>"Text", :description=>""}}
2.3.1 :073 > arr["Ford"]
=> {:type=>"Text", :description=>""}
2.3.1 :074 > arr["Ford"][:type]
=> "Text"
Both of the above examples are Ruby dictionaries / Hashes.
If you want to create a JSON from this, you will need to convert it:
2.3.1 :077 > require 'json'
=> true
2.3.1 :078 > arr.to_json
=> "{\"Ford\":{\"type\":\"Text\",\"description\":\"\"},\"BMW\":{\"type\":\"Text\",\"description\":\"\"},\"Fiat\":{\"type\":\"Text\",\"description\":\"\"}}"
This is a structure that makes more sense to me for accessing values based on known keys:
def create_fields fields
fields_hash = {}
fields.each do |field|
fields_hash[field] = {type: 'Text', description: ''}
end
fields_hash
end
# The hash for fields_hash will look something like this:
{
Ford: {
type: "Text",
description: ""
},
BMW: {...},
Fiat: {...}
}
This will allow you to access the values like so: fields[:Ford][:type] in ruby and fields.Ford.type in JSON. Sounds like it would be easier to return an Object rather than an Array. You can access the values based on the keys more easily this way, and still have the option of looping through the object if you want.
Obviously, there are several ways of creating or accessing your data, but I'd always lean towards the developer picking a data structure best suited for your application.
In your case currently, in order to access the Ford hash, you could use the Ruby Array#detect method as such:
ford = fields_list.detect{|field_hash| field_hash['field'] == 'Ford' }
ford['data'] # => {"type"=>"Text", "description"=>""}
ford['data']['type'] # => 'Text'
So, you have result of your method:
result =
[
{"field"=>"Ford", "data"=>{"type"=>"Text", "description"=>""}},
{"field"=>"BMW", "data"=>{"type"=>"Text", "description"=>""}},
{"field"=>"Fiat", "data"=>{"type"=>"Text", "description"=>""}}
]
to get 'Ford' from it you can use simple method detect
result.detect { |obj| obj['field'] == 'Ford' }
#=> { "field"=>"Ford", "data"=>{"type"=>"Text", "description"=>""}
Also I recommend you to edit your method to make it more readable:
def create_fields(fields)
fields.map do |field|
{
field: field,
data: {
type: 'Text',
description: ''
}
}
end
end
I have the following snippet of code to fetch certain columns from the db:
#data = Topic.select("id,name").where("id in (?)",#question.question_topic.split(",")).map(&:attributes)
In the resulting Array of Hashes which is :
Current:
#data = [ { "id" => 2, "name" => "Sports" }]
To be changed to:
#data = [ { "id" => "2", "name" => "Sports" }]
I want to convert "id" to string from fixnum. Id is integer in the db. What is the cleanest way to do this?
Note: After using .map(&:attributes) it is not an active record relation.
You can do it with proper map usage:
topics = Topic.select("id,name").where("id in (?)",#question.question_topic.split(","))
#data = topics.map do |topic|
{
'id' => topic.id.to_s,
'name' => topic.name
}
end
What you're looking for is simply
#data.each { |obj| obj["id"] = obj["id"].to_s }
There isn't really a simpler way (I think that's straightforward enough anyway).
Going by the title which implies a different question - converting every value in the hash to a string you can do this:
#data.each do |obj|
obj.map do |k, v|
{k => v.to_s}
end
end
Just leaving that there anyway.
You can use Ruby's #inject here:
#data.map do |datum|
new_datum = datum.inject({}) do |converted_datum, (key, value)|
converted_datum[key] = value.to_s
converted_datum
end
end
This will work to convert all values to strings, regardless of the key.
If you are using Rails it can be even cleaner with Rails' #each_with_object:
#data.map do |datum|
datum.each_with_object({}) do |(key, value), converted_datum|
converted_datum[key] = value.to_s
end
end
This will iterate all the key names in the hash and replace the value with the #to_s version of the datum associated with the key. nil's converted to empty strings. Also, this assumes you don't have complex data within the hash like embedded arrays or other hashes.
def hash_values_to_string(hash)
hash.keys.each {|k| hash[k]=hash[k].to_s}; hash
end
Is there a more elegant way to write this in Ruby, maybe using a loop?
def save_related_info
update_column(:sender_company_name, user.preference.company_name)
update_column(:sender_address, user.preference.address)
update_column(:sender_telephone, user.preference.telephone)
update_column(:sender_email, user.preference.email)
update_column(:sender_url, user.preference.url)
update_column(:sender_vat_number, user.preference.vat_number)
update_column(:sender_payment_details, user.preference.payment_details)
end
Thanks for any help.
Any reason you're not using update_attributes to do them all at once?
def save_related_info
update_attributes(
:sender_company_name => user.preference.company_name,
:sender_address => user.preference.address,
:sender_telephone => user.preference.telephone,
:sender_email => user.preference.email,
:sender_url => user.preference.url,
:sender_vat_number => user.preference.vat_number,
:sender_payment_details => user.preference.payment_details
)
end
def save_related_info
%w[company_name address telephone email url vat_number payment_details]
.each{|s| update_column("sender_#{s}".to_sym, user.preference.send(s))}
end
first guess is to put keys in and values in lists and then use loop. something like this:
keys = ['key1', 'key2', 'key3', 'key4']
values = [val1, val2, val3, val4]
keys.each_index do |i|
update_column(keys[i], values[i])
end
Minus in that approach is that the order of elements in values array should fit for order of keys. You could avoid it of using hash instead of arrays. Code will looks like this:
data = { "key1" => val1, "key2" => val2, "key3" => val3 };
data.each do |key, value|
update_column(keys, values)
end
I am trying this for the first time and am not sure I have quite achieved what i want to. I am pulling in data via a screen scrape as arrays and want to put them into a hash.
I have a model with columns :home_team and :away_team and would like to post the data captured via the screen scrape to these
I was hoping someone could quickly run this in a rb file
require 'open-uri'
require 'nokogiri'
FIXTURE_URL = "http://www.bbc.co.uk/sport/football/premier-league/fixtures"
doc = Nokogiri::HTML(open(FIXTURE_URL))
home_team = doc.css(".team-home.teams").map {|team| team.text.strip}
away_team = doc.css(".team-away.teams").map {|team| team.text.strip}
team_clean = Hash[:home_team => home_team, :away_team => away_team]
puts team_clean.inspect
and advise if this is actually a hash as it seems to be an array as i cant see the hash name being outputted. i would of expected something like this
{"team_clean"=>[{:home_team => "Man Utd", "Chelsea", "Liverpool"},
{:away_team => "Swansea", "Cardiff"}]}
any help appreciated
You actually get a Hash back. But it looks different from the one you expected. You expect a Hash inside a Hash.
Some examples to clarify:
hash = {}
hash.class
=> Hash
hash = { home_team: [], away_team: [] }
hash.class
=> Hash
hash[:home_team].class
=> Array
hash = { hash: { home_team: [], away_team: [] } }
hash.class
=> Hash
hash[:hash].class
=> Hash
hash[:hash][:home_team].class
=> Array
The "Hash name" as you call it, is never "outputed". A Hash is basically a Array with a different index. To clarify this a bit:
hash = { 0 => "A", 1 => "B" }
array = ["A", "B"]
hash[0]
=> "A"
array[0]
=> "A"
hash[1]
=> "B"
array[1]
=> "B"
Basically with a Hash you additionally define, how and where to find the values by defining the key explicitly, while an array always stores it with a numerical index.
here is the solution
team_clean = Hash[:team_clean => [Hash[:home_team => home_team,:away_team => away_team]]]