CODEWITHSUNDEEP
ruby
Black Sheep
Black Sheep

Reputation: 6694

Ruby - How to change an instance variable in various objects using map method

Lets have a class like this:

class Foo
  attr_accessor :var_1, :var_2, :var_3

  def initialize(var_1, var_2, var_3)
    @var_1 = var_1
    @var_2 = var_2
    @var_3 = var_3
  end
end

and now we create some objects:

a = Foo.new("c", 1, "d")
b = Foo.new("e", 2, "f")
c = Foo.new("g", 3, "h")

then we make an array with the new created objects:

array = [a, b, c]

And here where I'm stuck, I want to add a new value to an specific instance variable from object.

Example:

I try to change var_2 increased by one, but I don't know how to call or assign it to the instance variable var_2:

newArray = array.map { |x|

   x.var_1 + 1 # assign the new value to the instance variable 'var_2'
}

def showArray(array)

  array.each do | var |
    puts "Var 1: #{var.var_1} | Var 2: #{var.var_2} | Var 3: #{var.var_3}"
  end
end

showArray(newArray)

# desired output:
# => Var 1: c |  Var 2: 2 |  Var 3: d
# => Var 1: e |  Var 2: 3 |  Var 3: f
# => Var 1: g |  Var 2: 4 |  Var 3: h

I have to use the map method.

Upvotes: 1

Views: 1771

Answers (1)

Anthony
Anthony

Reputation: 15967

The issue you have is that your map function is returning the value of x.var_1 + 1 which is an Integer. When you loop back over it, you're looping over Integers not Foo objects.

You almost have it, you just need to use an assignment operator such as +=to assign val_2 to itself + 1 like this:

newArray = array.map { |x|
   x.var_2 += 1 
   x
}

def showArray(array)

  array.each do | var |
    puts "Var 1: #{var.var_1} | Var 2: #{var.var_2} | Var 3: #{var.var_3}"
  end
end

showArray(newArray)

output:

Var 1: c | Var 2: 2 | Var 3: d
Var 1: e | Var 2: 3 | Var 3: f
Var 1: g | Var 2: 4 | Var 3: h

Upvotes: 2

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