Simplify multiple if else condition in rails model

Question

I have to create logic for setting status of day which is based on multiple conditions. I started out by creating multiple if else statement but it does not feel right. Please help with right approach.

def set_status_of_day(late_policy,early_departure_policy)
        if late_policy.warning_on_late == "Half Day" && early_departure_policy.warning_on_late == "Half Day"
            self.status_of_day = "Absent"
        elsif late_policy.warning_on_late == "Half Day" && early_departure_policy.warning_on_late == "Present"
            self.status_of_day = "Half Day"
        elsif late_policy.warning_on_late == "Half Day" && early_departure_policy.warning_on_late == "Early Departure"
            self.status_of_day = "Half Day"
        elsif late_policy.warning_on_late == "Late" && early_departure_policy.warning_on_late == "Early Departure"
            self.status_of_day = "Half Day"
        elsif late_policy.warning_on_late == "Present" && early_departure_policy.warning_on_late == "Present"
            self.status_of_day = "Present"
        .
        .
        .
        .
        .
        .
        .
        end             
end

Thanks

guitarman · Accepted Answer · 2016-12-02 08:01:17Z

2

def set_status_of_day(late_policy, early_departure_policy)
  case [late_policy.warning_on_late, early_departure_policy.warning_on_late]
    when ["Half Day", "Half Day"] then "Absent"
    when ["Half Day", "Present"], ["Half Day", "Early Departure"], ["Late", "Early Departure"] then "Half Day"
    when ["Present", "Present"] then "Present"
    .
    .
    .
  end
end

I added the second when-line like Cary Swoveland suggested in the comments. The commas in the when clause work like an or-conjuction. See case in the docs for mor information.

edited Dec 2, 2016 at 8:01

answered Dec 1, 2016 at 12:18

guitarman

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2 Comments

Deepak Mahakale Over a year ago

I didn't know we can do this as well :O

Cary Swoveland Over a year ago

I suggest you add one more when/then clause, both to be complete (no ...) and to illustrate a useful construct: when ["Half Day", "Present"], ["Half Day", "Early Departure"], ["Half Day", "Late"] then "Half Day"

Oleksandr Holubenko · Accepted Answer · 2016-12-01 12:38:11Z

Just a bit bigger solution, but maybe it would be helpful

KEYS = {
  "Half Day" => 0,
  "Present" => 1,
  "Early Departure" => 2, 
  "Late" => 3
}

STATUSES = [
  { keys: [[0, 0]], value: "Absent" },
  { keys: [[0, 2], [2, 3], [0, 1]], value: "Half Day" },
  { keys: [[1, 1]], value: "Present" }
]

def status(late_warning, early_warning)
  result = STATUSES.find { |status| status[:keys].include? [KEYS[late_warning], KEYS[early_warning]] } || { value: 'Unknown'} 
  result[:value]
end

# For example:
# status("Half Day", "Half Day")
#=> "Absent"
#
# status("Half Day", "Half D")
#=> "Unknown" 


def set_status_of_day(late_policy,early_departure_policy)
  self.status_of_day = status(late_policy.warning_on_late, early_departure_policy.warning_on_late)            
end

Eric Duminil · Accepted Answer · 2016-12-01 17:35:22Z

You could assign values (0 for start of the day, 1 for end of the day, ...) and calculate the length of the day (close to 0 is "Absent", close to 1 is "Present").

@morning_hash = {
  "Present"  => 0.0,
  "Late"     => 0.25,
  "Half Day" => 0.5,
}

@afternoon_hash = {
  "Half Day" => 0.5,
  "Early"    => 0.75,
  "Present"  => 1.0,
}

def duration_description(morning, afternoon)
  duration = @afternoon_hash[afternoon]-@morning_hash[morning]
  case duration
    when 0...0.25   then "Absent"
    when 0.25..0.75 then "Half Day"
    when 0.75..1.0  then "Present"
  end
end

puts duration_description("Half Day", "Half Day") == "Absent"
puts duration_description("Half Day", "Present")  == "Half Day"
puts duration_description("Half Day", "Early")    == "Half Day"
puts duration_description("Late", "Early")        == "Half Day"
puts duration_description("Present", "Present")   == "Present"

#=> true true true true true

~

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