ekanade def identify_class(obj) case obj when Hacker,Submission,TestCase,Contest puts "It's a #{obj.class}!" else puts "It's an unknown model" end end
this works incase someone is looking for different solutions.
ksam95 Can you explain?
keithchongwy he is using interpolation within the double quoted strings. Hence obj.class will be processed or evaluated first before it turns into a string. (respectively in order: "Hacker", "Submission", "TestCase", and then "Contest")
as soon as he grouped the whens in the case, it is almost as if he is saying
if obj == Hacker || obj == Submission || obj == TestCase || obj == Contest puts "It's a #{obj.class}!" else puts "It's an unknown model"
Here is the unrefactored version
write your case control structure here
case obj when Hacker puts "It's a Hacker!" when Submission puts "It's a Submission!" when TestCase puts "It's a TestCase!" when Contest puts "It's a Contest!" else "It\'s an unknown model" endend
dongxialiu2002 it won't pass the test case 1
phillipr360 This problem statement is extremely misleading and needs to be rewritten.
As it is stated, we are lead to believe that Hacker, Submission, TestCase, and Constants are all separate classes inheriting from the same superclass. This means that the following solution should work:
case obj when Hacker, Submission, TestCase, Contest puts "It's a #{obj.class}!" else puts "It's an unknown model" end
However, it fails test case 1. Moreover, some of the solutions listed below suggest that Hacker, Submission, TestCase, and Constant are really integer constants euqivalent to to 1, 2, 3, and 4.
Obviously, using integer constants instead of subclasses goes against the problem definition (as currently written). While it will work for basic solutions checking each class type separately, more elaborate solutions taking advantage of the obj.class value will fail. Moreover, testing one solution using subclasses and another using integer constants is extremely misleading; if our solution is expected to work for both situations, the problem statement should explicitly say so.
machadolopes def identify_class(obj)this code worked fine on IRB passing the input via method like so: identify_class(10), identify_class(3), etc But it's not working here.
# write your case control structure here
case obj
when 1
puts "It's a Hacker!"
when 2
puts "It's a submission!"
when 3
puts "It's a TestCase!"
when 4
puts "It's a Contest!"
else
puts "It's an unknown model"
end
end
jrcharney I know right. The input for this example screws up everything!
kishancs46 Why does this work?
case obj when Hacker, Submission, TestCase, Contest puts "It's a #{obj.class}!" else puts"It's an unknown model" endWhen "k" == String it says false,
"k" === String is also false
what is the case logic in ruby?
dimitrynazarov [deleted]dimitrynazarov Got the same solution and its failing on every test case. Can't figure out what's happening:
def identify_class(obj) case obj when "Hacker", "Submission", "TestCase", "Contest" puts "It\'s a #{obj}!" else puts "It\'s an unknown model" end end
gettting correct reuturns when running it locally:
identify_class('Hacker') identify_class('Submission') identify_class('TestCase') identify_class('Submission') identify_class('Contest')
dimitrynazarov mmann, I fall in the same trap all the time. Jumping into writing code without reading and fully understanding the task first. We're asked to identify
classes, notstrings
dipakpurbey use directly the class name instead of it as string.. Hacker instead of "Hacker"
sweetmannc999 try this
def identify_class(obj) case obj.class.to_s when "Hacker", "Submission", "TestCase", "Contest" puts "It's a #{obj.class}!" else puts "It's an unknown model" end end
jueluddin39 because "Hacker", "Submission", "TestCase", "Contest" are not strings.
ahmadhasankhan Try this.
def identify_class(obj) # write your case control structure here case obj.class.to_s when "Hacker" puts "It's a Hacker!" when "Submission" puts "It's a Submission!" when "TestCase" puts "It's a TestCase!" when "Contest" puts "It's a Contest!" else puts "It's an unknown model" end end
lyc950421 This works .. thx
ChristianVelez This answer certainly works but the idea of turning a class into a string could lead to potential issues down the line and made me a bit uncomfortable.
This worked for me in case anyone is interested:
def identify_class(obj) case obj when Hacker puts "It\'s a Hacker!" when Submission puts "It\'s a Submission!" when TestCase puts "It\'s a TestCase!" when Contest puts "It\'s a Contest!" else puts "It\'s an unknown model" end end
lynnshep89 I did this same thing, yet I am not passing both Test Cases.
ahmadhasankhan Hey @ChristianVelez, will you please elaborate how turning a class name into a string could lead to potential issues ?
ahmadhasankhan [deleted]
mail_vivekr obj.class.to_s means....what is to_s
collinhurst12 to string
forevertkj4 can you explain, why that code its work ?
danielgcwik it worked for me thanks
bazzargh case comparisons are done using
===, so this is the same asif Hacker === obj ...(and so on). The===method ofClassis inherited fromModule, and is documented as:"Returns true if obj is an instance of module or one of module 's descendants. Of limited use for modules, but can be used in case statements to classify objects by class."
So it's also asymmetric -
"k" === Stringis false, butString === "k"is true.
saurabh03 I tried solving this by NOT using the case statement. I did something like this
def identify_class(obj)if !obj.nil? && ['Hacker', 'Submission', 'TestCase', 'Contest'].include?(obj.class.to_s) puts("It\'s a #{obj.class}!") else puts("It\'s an unknown mode!") end
endThis works for general test case but fails for the hidden one. Any pointers what is causing this failure?
saurabh03 Please ignore it, fault was the typo at the end. I should have written 'model' instead of 'mode!'
MoonWalkerPTAsked to answer Jesus!... you could just use a case statement. It's easier, a lot!
saurabh03 Yes no particular reason for not using the recommended 'case' statement.
p0lym4th Why isn't it
case obj.class?
artur_ludwik def identify_class(obj) case obj when Hacker puts "It's a Hacker!" when Submission puts "It's a Submission!" when TestCase puts "It's a TestCase!" when Contest puts "It's a Contest!" else puts "It's an unknown model" end end
igorp984 This is my code, pass in the 1 test but not pass in the test 2. When Hacker{-truncate-} the expected output is "It's a Submission". Please, help me understand
def identify_class(obj) case obj when Hacker puts "It's a Hacker!" when Submission puts "It's a Submission!" when TestCase puts "It's a TestCase!" when Contest puts "It's a Contest!" else puts "It's an unknown model!" end end
abdellani For me, those two code are equivalent, but in practice the first one works, but the second doesn't, it falls into the default case. I was obliged to convert obj.class to string
if obj.class == Hacker or obj.class == Submission or obj.class ==TestCase or obj.class == Contest puts "It's a #{obj.class.to_s}!" else puts "It's an unknown model" end
the second
case obj.class when Hacker,Submission,TestCase,Contest puts "It's a #{obj.class.to_s}!" else puts "It's an unknown model" end
abdellani I found an answer. case .. when behave as "===" and not "==". The equivalent code is :
if obj.class === Hacker or obj.class === Submission or obj.class ===TestCase or obj.class === Contest puts "It's a #{obj.class.to_s}!" else puts "It's an unknown model" end
sjoysos I was confused with "..Ruby to identify the class to which the object belongs..." and was using type(obj) to get class of object, not sure if i was reading it wrong or the question could be written better
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