My question model holds the prompt and the answer choices for questions that students can answer. It includes columns named :choice_0, :choice_1, :choice_2, :choice_3, :choice_4, and :choice_5.
In one section of my controller, I've used the following code:
correct_array.push(these_params[:choice_0]) if !these_params[:choice_0].blank?
correct_array.push(these_params[:choice_1]) if !these_params[:choice_1].blank?
correct_array.push(these_params[:choice_2]) if !these_params[:choice_2].blank?
correct_array.push(these_params[:choice_3]) if !these_params[:choice_3].blank?
correct_array.push(these_params[:choice_4]) if !these_params[:choice_4].blank?
correct_array.push(these_params[:choice_5]) if !these_params[:choice_5].blank?
In other areas of my app, I've used the #{} syntax, for example:
params[:choice_#{n}]
But that doesn't work within a params hash for some reason. I'm sure that there is a drier way to accomplish these five lines.
Thank you in advance for any insight.
A more Ruby way to do this is:
correct_array = (0..5).map { |i| these_params["choice_#{i}".to_sym] }.select(&:present?)
Or as a method:
def correct_array
(0..5).map { |i| these_params["choice_#{i}".to_sym] }.select(&:present?)
end
In either case, you have the added bonus of not having to initialize correct_array as it is created on the fly.
You may try this
(0..5).each do |i|
param_i = these_params["choice_#{i}".to_sym]
correct_array.push(param_i) if param_i.present?
end
Related
Below is my Pokemon TCG API key
I have read the documentation but I cannot find a way to retrieve the data I need which is the images of each card in a set. If anyone can help with or give me any pointers on how to retrieve this I would greatly appreciate it.
https://github.com/PokemonTCG/pokemon-tcg-sdk-ruby/blob/master/README.md
This above is the link to the documentation on Github.
Pokemon.configure do |config|
config.api_key = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
end
sets = Pokemon::Set.where(q: 'legalities.standard:legal').first
p sets
I am expecting to retrieve specific data from the Pokemon TCG API which from above should be within these Ruby classes.
p sets.images.symbol will print out the link to:
"https://images.pokemontcg.io/swshp/symbol.png"
p sets.images.logo will print out the link to:
"https://images.pokemontcg.io/swshp/logo.png"
When you are unsure what is contained within the class you're getting, in this case a Pokemon::Set class, you may see all the methods of this resulting variable with sets.methods.sort.each{|m| p m}, there you'll find the images method and can dig deeper to symbol and logo.
In your example you are searching for sets. In case of cards:
cards = Pokemon::Card.where(page: 5, pageSize: 100)
cards.each{|card| p card.images.large}
This will print out all the links to large cards.
Update
Clarification based on comments
How to print out methods and how to know which class you are referring to.
Let's start with you code snippet:
sets = Pokemon::Set.where(q: 'legalities.standard:legal').first
puts sets.class
Output:
Pokemon::Set
It would be more clear if you name your variable as set because you're selecting the .first element of an array.
Back to my cards example:
cards = Pokemon::Card.where(page: 5, pageSize: 100)
puts cards.class
Output:
Array
As I did not select any item from the array cards naming makes perfect sense, and this array will contain a card:
card = cards.first
puts card.class
Output
Pokemon::Card
Printing methods
So, given we are now well aware of class each variable contains and what we are referring to, we are ready to print out the methods for both:
sets.methods.sort.each{|method| p method}
cards[0].methods.sort.each{|method| p method}
Output:
…
:hash
:hp
:hp=
:id
:id=
:images <== Here!
:images=
:inspect
:instance_eval
:instance_exec
:instance_of?
…
Once again, mind the [0] selection of the first item. When we want to know methods, we want to know it either for Pokemon::Set or Pokemon::Card.
I'm building a site with users in all 50 states. We need to display information for each user that is specific to their situation, e.g., the number of events they completed in that state. Each state's view (a partial) displays state-specific information and, therefore, relies upon state-specific calculations in a state-specific model. We'd like to do something similar to this:
##{user.state} = #{user.state.capitalize}.new(current_user)
in the users_controller instead of
#illinois = Illinois.new(current_user) if (#user.state == 'illinois')
.... [and the remaining 49 states]
#wisconsin = Wisconsin.new(current_user) if (#user.state == 'wisconsin')
to trigger the Illinois.rb model and, in turn, drive the view defined in the users_controller by
def user_state_view
#user = current_user
#events = Event.all
#illinois = Illinois.new(current_user) if (#user.state == 'illinois')
end
I'm struggling to find a better way to do this / refactor it. Thanks!
I would avoid dynamically defining instance variables if you can help it. It can be done with instance_variable_set but it's unnecessary. There's no reason you need to define the variable as #illinois instead of just #user_state or something like that. Here is one way to do it.
First make a static list of states:
def states
%{wisconsin arkansas new_york etc}
end
then make a dictionary which maps those states to their classes:
def state_classes
states.reduce({}) do |memo, state|
memo[state] = state.camelize.constantize
memo
end
end
# = { 'illinois' => Illinois, 'wisconsin' => Wisconsin, 'new_york' => NewYork, etc }
It's important that you hard-code a list of state identifiers somewhere, because it's not a good practice to pass arbitrary values to contantize.
Then instantiating the correct class is a breeze:
#user_state = state_classes[#user.state].new(current_user)
there are definitely other ways to do this (for example, it could be added on the model layer instead)
I am new to Ruby, so let me describe the context of my problem first:
I have a json as input which has the following key / value pair:
{
"service": "update"
}
The value has many different values for example: insert,delete etc.
Next there is a method x which handles the different requests:
def x(input)
case input[:service]
services = GenericService.new
when "update"
result = services.service(UpdateService.new,input)
when "insert"
result = services.service(InsertService.new,input)
when "delete"
result = services.service(DeleteService.new,input)
....
....
else
raise "Unknown service"
end
puts JSON.pretty_generate(result)
end
What is bothering me is that I still need to use a switch statement to check the String values (reminds me of 'instance of' ugh..). Is there a cleaner way (not need to use a switch)?
Finally I tried to search for an answer to my question and did not succeed, if however I missed it feel free to comment the related question.
Update: I was thinking to maybe cast the string to the related class name as follows: How do I create a class instance from a string name in ruby? and then call result = services.services(x.constantize.new,input) , then the class names ofcourse needs to match the input of the json.
You can try something like:
def x(input)
service_class_name = "#{input[:service].capitalize}Service"
service_class = Kernel.const_get(service_class_name)
service_class.new(input).process
end
In addition you might want to check if this is a valid Service class name at all.
I don't understand why you want to pass the service to GenericService this seems strange. let the service do it's job.
If you're trying to instatiate a class by it's name you're actually speaking about Reflection rather than Polymorphism.
In Ruby you can achieve this in this way:
byName = Object.const_get('YourClassName')
or if you are in a Rails app
byName= 'YourClassName'.constantize
Hope this helps
Just first thoughts, but you can do:
eval(services.service("#{input[:service].capitalize}Service.new, #{input})") if valid_service? input[:service]
def valid_service?
w%(delete update insert).include? input[:service]
end
As folks will no doubt shout, eval needs to be used with alot of care
I saw several variations of this question but did not really find a solid answer.
So I have an array of URLS. I want to loop through that array and for each individual URL, I would create an instance of class WebPages.
So if array URLS has 5 urls in it, then I would create 5 objects of WebPages. I tried to use eval() to do this but quickly learned that the instances made by eval have a very local scope and I cannot use those WebPage objects after.
string_to_eval = #urls.map{|x| "webpage#{urls.index(x)} = WebPage.new('# {x}')"}.join(';')
puts string_to_eval
eval(string_to_eval)
String_to_eval prints out:
webpage0 = WebPage.new('http://www.google.com');
webpage1 = WebPage.new('http://www.yahoo.com');
webpage2 = WebPage.new('http://www.amazon.com');
webpage3 = WebPage.new('http://www.ebay.com')
How else can I make an object with each iteration of the loop in Ruby? Is there a way around this?
Why not just this?
webpages = #urls.map { |url| WebPage.new(url) }
It is generally a bad idea to have webpage0, webpage1... when you can have webpages[0], webpages[1]... (Also, the array way does not require the Evil of eval.)
In this situation I would forgo unique variable names and instead simply leave the resulting objects in an array. In that case the code would look like this:
>> #urls.map{|url| WebPage.new(url)}
=> [WebPage('http://www.google.com'), WebPage('http://www.yahoo.com'), WebPage('http://www.amazon.com'), WebPage('http://www.ebay.com') ]
How do I create an object if one is not found? This is the query I was running:
#event_object = #event_entry.event_objects.find_all_by_plantype('dog')
and I was trying this:
#event_object = EventObject.new unless #event_entry.event_objects.find_all_by_plantype('dog')
but that does not seem to work. I know I'm missing something very simple like normal :( Thanks for any help!!! :)
find_all style methods return an array of matching records. That is an empty array if no matching records are found. And an empty is truthy. Which means:
arr = []
if arr
puts 'arr is considered turthy!' # this line will execute
end
Also, the dynamic finder methods (like find_by_whatever) are officially depreacted So you shouldn't be using them.
You probably want something more like:
#event_object = #event_entry.event_objects.where(plantype: 'dog').first || EventObject.new
But you can also configure the event object better, since you obviously want it to belong to #event_entry.
#event_object = #event_entry.event_objects.where(plantype: 'dog').first
#event_object ||= #event_entry.event_objects.build(plantype: dog)
In this last example, we try to find an existing object by getting an array of matching records and asking for the first item. If there are no items, #event_object will be nil.
Then we use the ||= operator that says "assign the value on the right if this is currently set to a falsy value". And nil is falsy. So if it's nil we can build the object form the association it should belong to. And we can preset it's attributes while we are at it.
Why not use built in query methods like find_or_create_by or find_or_initialize_by
#event_object = #event_entry.event_objects.find_or_create_by(plantype:'dog')
This will find an #event_entry.event_object with plantype = 'dog' if one does not exist it will then create one instead.
find_or_initialize_by is probably more what you want as it will leave #event_object in an unsaved state with just the association and plantype set
#event_object = #event_entry.event_objects.find_or_initialize_by(plantype:'dog')
This assumes you are looking for a single event_object as it will return the first one it finds with plantype = 'dog'. If more than 1 event_object can have the plantype ='dog' within the #event_entry scope then this might not be the best solution but it seems to fit with your description.