The Sunspot gem for Solr has a method that requires a block with 2 elements:
search.each_hit_with_result do |hit,result|
and I'm using it to build a new hash of results like so:
results = Hash.new
search.each_hit_with_result do |hit,result|
results[result.category.title] = hit.score
end
This is cool and everything but I can't help thinking there is a more 'ruby' way of doing it and I've been looking at the awesome inject method. I think something like the following should be possible but I can't get it to syntactically work. Anyone got any ideas?
search.each_hit_with_result.inject({})
{|newhash,|hit,result||newhash[result.category.title]=hit.score}
I believe that method looks like what do you want:
search.each_hit_with_result.inject({}) { |new_hash, current| new_hash[current[0]] = current[1]; new_hash }
Hope its help you.
Object#enum_for is designed exactly for this:
hit_results = search.enum_for(:each_hit_with_result)
results = Hash[hit_results.map { |hit, res| [res.category.title, hit.score] }]
In my opinion, code should never expose each_xyz methods, they promotes smelly imperative code (as you rightly detected). That kind of methods were understandable when there were no enumerators and you needed to return data lazily, but now it should be considered an anti-pattern. They should return an enumerable or enumerator and let the user decide how to use it.
Related
I'm trying to implement and Authorization module, because currently the authorization logic for a certain resource is separated on two or three different places and even though I'm not sure this is the best approach, at least I think it will provide some encapsulation.
Since I'm checking for several different things
Does the user have the right role
Is the resources in the right state to process the required action
Do the user has the right to perform the required action on this particular resource
So as you can see, there are several checks, I'm not pretending to be completely correct here, but this is pretty close to the real case, so I've decided to use something like a Result Object even though it's actually not an object but a struct and I'm not using Gem but pretty simple custom implementation.
So part of my Authorization module is this:
module Authorization
Result = Struct.new(:successfull?, :error)
extend self
def read(user, resource, message: 'Permission denied')
can_read =
[
condition1,
condition2,
condition3
]
return Result.new(can_read.any?, can_read.any? ? nil : message))
end
However within this Authorization module I have a lot of methods and some of them check read internally like so:
def assign(user, resource, message: 'Permission denied')
return read(user, resource) unless read(user, resource).successfull?
Result.new(true, nil)
end
So my main question is how to avoid this double call to read(user, resource). I guess one option would be to just call it before the check like:
result = read(user, resource)
return result unless result.successfull?
However I'm pretty new to Ruby and I suspect that maybe there is more ruby-like way to do this. Just to inline it somehow by assigning the result from read inside the condition check...However this is just wild guess.
And one more question, that came up while I was writing this. Currently if I want to send nil for message when the authorization passes I'm doing this:
return Result.new(can_read.any?, can_read.any? ? nil : message))
Because message unless can_read.any? is throwing and error even though I thought it would default to nil. So again, is there some more ruby-like way to do this?
First part can be written with Object#yield_self:
def assign(user, resource, message: 'Permission denied')
read(user, resource).yield_self do |res|
res.successful? ? Result.new(true, nil) : res
end
end
successfull? -> successful? for English reasons. I am not convinced this is more readable than using a local variable though. Alternatively:
(res = read(user, resource)).successful? ? Result.new(true, nil) : res
As for your second question, you'll need more parentheses
Result.new(can_read.any?, (message if can_read.none?))
the return is not needed.
I would also advise you to slow down with all the unlesses, try to swap your conditions to if whenever possible -- I find it quite useful to make Result a class and define a failed? method for it. Actually, I'd consider this:
class Result
def initialize(error)
#error = error
end
def successful?
#error.nil?
end
def failed?
!successful?
end
end
That depends on how complicated your Result gets, but for the use case shown, it would be a little cleaner imho.
This method works, but I'm sure the performance could be greatly improved. Also, I'm realizing how fun and awesome it is to take smelly code like this, and rubify it. But I need a little more help to get my Ruby skills to the level to refactor something like this.
An objective can have "preassign" objectives. These are pre-requisites that must be completed before the a student can try the objective in question.
ObjectiveStudent is the join model between an objective and a student. It has a method called "points_all_time" that finds the student's best score on that objective.
The check_if_ready method is the one that I'm trying to refactor in this question. It also belong to the ObjectiveStudent model.
It needs to check whether the student has passed ALL of the preassigns for a given objective. If so, return true. Return false if the student has a less-than-passing score on any of the preassigns.
def check_if_ready
self.objective.preassigns.each do |preassign|
obj_stud = self.user.objective_students.find_by(objective_id: preassign.id)
return false if obj_stud.points_all_time < 7
end
return true
end
Right now I suspect this method is making too many calls to the database. What I'm really hoping to find is some way to look at the scores for the pre-reqs with a single db call.
Thank you in advance for any insight.
The following should work for you:
def is_ready?
user.objective_students
.where(objective_id: objective.preassigns.select(:id))
.none? { |obj_stud| obj_stud.points_all_time < 7 }
end
We collect all the objective_students for the user where the objective_id is in the list of objective.preassigns ids. This results in one 1 query being executed.
Then we use Enumerable#none? to make sure that none of the objective_students have points_all_time less than 7.
You could also use the inverse .all? { |obj_stud| obj_stud.points_all_time >= 7 } if you wanted
One way you could "rubify" this method is to rewrite the signature as:
def is_ready?
It is common practice to append ? to functions that return a boolean value in Ruby. (Note: I also don't really see a reason to have the word 'check' in the declaration, but that's just an opinion).
Furthermore, if objective_id is the primary key for the objective_students model, you can simply write objective_students.find(preassign.id) instead of the find_by method.
I would also suggest having a separate method for returning a student's points (especially since I suspect you will need to get a student's points more than just once) :
def getPoints(preAssignId)
return self.user.objective_students.find_by(objective_id: preAssignId).points_all_time
end
Then your main method can be written in a more clear, self-describing manner as:
def is_ready?
self.objective.preassigns.each {|preassign| return false if getPoints(preassign) < 7 }
return true
end
For example, say I want to do this:
{
:mytime => times[:mytime]
}
There is a bit of repetition here, is it possible to just do something like { :mytime => times[$_key] } (made up syntax)?
The short answer is: no, there's no syntax that does anything like that. Without more context about what you're actually trying to do, there isn't really a good longer answer. Still, I'll try to be a little more useful. If you're really worried about repetition, you could do something like:
h = {}
[:mytime, :yourtime].each do |k|
h[k] = times[k]
end
For only a few keys, I can't see that being worth it, personally.
I am tring to assign a value to ViewBag in the controller for later usage in the View, It complaines with the following error.
Assigning the value in the Controller like this.
ViewBag["isAdmin"]=true;
Error:
Cannot apply indexing with [] to an expression of type 'System.Dynamic.DynamicObject'
Does anyone had this before?
All you need is ViewBag.isAdmin = true. the you can access is with
if(ViewBag.isAdmin)
{
//do stuff
}
As a follow-up, the idea behind ViewBag (and ViewData) is that you can store off key-value pairs of stuff and conveniently access them over in the View.
With ViewData, you reference these things like so:
ViewData["SomeKey"] = someObject;
If you want to do the same using the ViewBag instead (which provides a wrapping around that ViewData dictionary construct and makes it a little less verbose and a bit more readable) you reference things like so:
ViewBag.isAdmin = true;
and can check them, as tyrongower stated above, like so:
if (ViewBag.isAdmin)
{
// do stuff
}
I typically use the ViewBag syntax when I do use this construct, but they really do reference the same stuff. So if you did something like so outside the View:
ViewData["isAdmin"] = true;
you could reference it like this, if you were so inclined:
ViewBag.isAdmin
or vice-versa.
Just a little more detail on the concept.
Right now the code below produces the output below it, but how would I override the default output to a more logical one for my given situation. I understand that I could just append the string "Hz" after the range but I want to incorporate this into a module which can be included to the Range class when needed or for use with refinements.
Code:
("20Hz"..."40Hz").each { |hz| p hz }
Output:
"20Hz"
"20Ia"
"20Ib"
...etc
Wanted output:
"20Hz"
"21Hz"
"22Hz"
...etc
This is absolutely a bad idea, but just for the sake of experimenting:
class String
alias_method :succ_orig, :succ
def succ
self.gsub(/\d+/, &:succ_orig)
end
end
p ("20Hz".."40Hz").to_a
#=> ["20Hz", "21Hz", "22Hz", "23Hz", "24Hz", "25Hz", "26Hz", "27Hz", "28Hz", "29Hz", "30Hz", "31Hz", "32Hz", "33Hz", "34Hz", "35Hz", "36Hz", "37Hz", "38Hz", "39Hz", "40Hz"]
As you can see, it is not the Range class that should be altered, but String#succ method.
But in real project, you better create a class for your Hertz-strings and define its succ method appropriately.
I think its quite simple.
("20"..."40").each { |hz| p hz + 'Hz'}
I would recommend creating your own function or class for this rather that changing the way in which Ruby ranges behave. There is probably a lot of other code that depends on ranges working in a specific way, and changing the range definition would result in that code breaking. You might want to aim for something like this:
HzRange.new("20Hz", "40Hz").each{ |hz| p hz }
The creation of the HzRange class is up to you, but you should probably delegate to the Array or Range object so that you can inherit some default behavior like Enumerable.