Subtraction in Rails

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Subtraction in Rails



I am very new to Rails and currently face an issue about subtraction in Rails. I have an object that has an integer type of attribute but I want to subtract 1 from the attribute after finishing a particular action but I am getting NoMethodError (undefined methodto_i' for [40]:Arrayerror and when I removedto_iit is saying-` is not a method. Is there any way that I can update the stored value?


NoMethodError (undefined method


error and when I removed


it is saying



Here is what I have tried:



Controller


def subtraction
#find a item and get the value, let's say value is 40
item = Item.where(id: params[:id]).pluck(:value)

# subtract 1 from the value and i thought it would be 40-1
after_subtraction = item.to_i - 1

#update the value
final = item.update(value: after_subtraction)
end




2 Answers
2



You can't directly convert array in to to_i . please use below method


after_subtraction = item.join.to_i - 1



The better way to handle is


item = Item.find_by(id: params[:id]).value



pluck will return you array, which is not necessary in your case here.






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