I have an array short_code[] that contains an array of short product identifiers such as ["11111", "2222", "33333"]
I want to create a copy of the array that contains the corresponding 'long code' data:
long_code[i] = my_lookup_long_code(short_code[i])
While simple iteration is easy, I'm wondering, as a relative ruby newbie, what is the 'ruby way' to create an array which is a simply method() applied on every element in the original array?
You can use the map command, which will return a new array with the results of your code block:
long_code = short_code.map{ |code| my_lookup_long_code(code) }
Related
Firstly I have an array of multiple objects [#<Vgpop::Game:0x00007fcd5b246a00 #name="Super Smash Bros. Ultimate", #console=nil, #score=nil>....]
Then I have an array of my consoles that looks like this: ["Nintendo Switch"...]
How do I map the values from my second array to my object array so that the return is:
[#<Vgpop::Game:0x00007fcd5b246a00 #name="Super Smash Bros. Ultimate", #console="Nintendo Switch", #score=nil>....]
Seems like we can come up with this solution my friend:
first_array.each_with_index { |vgpop, i| vgpop.name = second_array[i] }
Given this hash:
hash1= { node1: { node2: { node3: { node4: { node5: 1 } } } } }
We access inside nodes with square brackets like this:
hash1[:node1][:node2][:node3][:node4]
Now I have a hash that I know will always be nested as it is an XML response from a SOAP webservice, but neither the depth of the hash nor the names of the nodes stay the same. So it would be nice if I could ask the user of my application for the hash depth and store it in a variable. And then be able to do hash1[:hash_depth] and achieve the same result as above.
I have accomplished what I want by the following code:
str = 'node1,node2,node3,node4'
str_a = str.split(',')
hash_copy = hash1
str_a.each { |s| hash_copy = hash_copy.[](s.to_sym) }
hash_copy
=> {:node5=>1}
hash1[:node1][:node2][:node3][:node4]
=> {:node5=>1}
that is asking the user to enter the hash depth separated by commas, store it in a string, split it, make an array, clone the original hash, go down each level and modify the hash till I get to the desired node. Is there a way to do it with the square brackets notation and using a variable to store the depth without modifying the hash or needing to clone it?
Edit:
someone answered with the following (can't see his post anymore???)
hash_depth="[:node1][:node2][:node3][:node4]"
eval "hash1#{hash_depth}"
Although eval does everything you need, there is another approach, since you already have the working code for comma-separated list:
hash_depth="[:node1][:node2][:node3][:node4]"
csh = hash_depth.gsub(/\A\[:|\]\[:|\]\Z/, { '][:' => ',' })
#⇒ "node1,node2,node3,node4"
And now you are free to apply your existing function to csh.
If this is a webapp, I think you should prepare a list of short textareas, which starts with a single text item, and the user can keep adding a new item to the list by clicking on a button. The areas will be filled by the user, and will be sent.
Then, you will probably receive this through some serialized form. You decode this to get an array of strings:
str_a = ["node1", "node2", "node3", "node4"]
and you can reach the inner element by doing:
str_a.inject(hash1){|h, s| h[s.to_sym]} #=> {:node5 => 1}
I have an array of strings (actually file names), something like
filenames = ['file1.jpg', 'file2.jpg', 'file3.jpg']
The method I am calling expects something like
images = Magick::ImageList.new("image1.png", "image2.png", "image3.png")
but if I call as below, I am actually passing an array.
images = Magick::ImageList.new(filenames)
How do I unwrap the contents of the array?
Do as below using splat opearator(*) :
images = Magick::ImageList.new(*filenames)
As #Stefan mentioned the documentation link for the same Array to Arguments Conversion
I'm using the Foursquare API, and I want to extract the "id" value from this hash
[{"id"=>"4fe89779e4b09fd3748d3c5a", "name"=>"Hitcrowd", "contact"=>{"phone"=>"8662012805", "formattedPhone"=>"(866) 201-2805", "twitter"=>"hitcrowd"}, "location"=>{"address"=>"1275 Glenlivet Drive", "crossStreet"=>"Route 100", "lat"=>40.59089895083072, "lng"=>-75.6291255071468, "postalCode"=>"18106", "city"=>"Allentown", "state"=>"Pa", "country"=>"United States", "cc"=>"US"}, "categories"=>[{"id"=>"4bf58dd8d48988d125941735", "name"=>"Tech Startup", "pluralName"=>"Tech Startups", "shortName"=>"Tech Startup", "icon"=>"https://foursquare.com/img/categories/shops/technology.png", "parents"=>["Professional & Other Places", "Offices"], "primary"=>true}], "verified"=>true, "stats"=>{"checkinsCount"=>86, "usersCount"=>4, "tipCount"=>0}, "url"=>"http://www.hitcrowd.com", "likes"=>{"count"=>0, "groups"=>[]}, "beenHere"=>{"count"=>0}, "storeId"=>""}]
When I try to extract it by using ['id'], I get this error can't convert Symbol into Integer. How do I extract the value using ruby? Also, how do I do this for multiple hashes extracting the "id" value each time?
Please pardon my inexperience. Thanks!
It's wrapped in an array, that's what the [ and ] mean on the start and end. But it also looks like this array only one object in it, which is the hash you really want.
So assuming you want the first object in this array:
mydata[0]['id'] # or mydata.first['id'] as Factor Mystic suggests
But usually when an API returns an Array there is a reason (it might return many results instead of just one), and naively plucking the first item from it my not be what you want. So be sure you are getting the kind of data you really expect before hard coding this into your application.
For multiple hashes, if you want to do something with the id (run a procedure of some kind) then
resultsArray.each do |person|
id = person["id"] #then do something with the id
end
If you want to just get an array containing the ids then
resultsArray.map{|person| person["id"]}
# ["4fe89779e4b09fd3748d3c5a", "5df890079e4b09fd3748d3c5a"]
To just grab the one item from the array, see Alex Wayne's answer
To get an array of ids, try: resultsArray.map { |result| result["id"] }
My code looks like this:
a = IO.readlines("input.txt").map { |line| Vector.[](line.split) }
Now I want to access a single component of the first vector within my a array. I'm writing the following to address a vector:
puts a[0]
The behavior is pretty much expected - I receive the following:
Vector[1.2357, 2.1742, -5.4834, -2.0735]
Now let's try to address a single component this way:
puts a[0][0]
and voila, I receive a list of all the vector components,like:
1.2357
2.1742
-5.4834
-2.0735
How come? Maybe the last attempt was wrong? How do I correctly address a scalar inside a vector within an array?
Due to your code I think the array construction should be:
a = IO.readlines("input.txt").map { |line| Vector[*line.split] }