Which of the following is a valid way to group an array nums by whether elements are positive or negative using group_by returning :positive or :negative?

easy📝 Conceptual Q2 of 15

Ruby - Enumerable and Collection Processing

Which of the following is a valid way to group an array nums by whether elements are positive or negative using group_by returning :positive or :negative?

Anums.group_by { |n| n > 0 ? :positive : :negative }

Bnums.group_by(&:positive?)

Cnums.group_by { |n| n if n > 0 }

Dnums.group_by { |n| n > 0 }

Step-by-Step Solution

Solution:

Step 1: Understand grouping by condition
We want to group by positive or negative, so the block should return a symbol or label for each element.
Step 2: Check each option's block return value
nums.group_by { |n| n > 0 ? :positive : :negative } returns :positive or :negative explicitly, which is clear and correct. nums.group_by(&:positive?) calls a method that returns true/false but does not distinguish negative. nums.group_by { |n| n if n > 0 } returns nil for negatives, which is not a proper group key. nums.group_by { |n| n > 0 } returns true/false but does not label groups clearly.
Final Answer:
nums.group_by { |n| n > 0 ? :positive : :negative } -> Option A
Quick Check:
group_by block returns clear group keys = nums.group_by { |n| n > 0 ? :positive : :negative } [OK]

Quick Trick: Use clear labels in group_by block for distinct groups [OK]

Common Mistakes:

Returning nil in block
Using methods that don't distinguish groups
Returning boolean without labels

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Which of the following is a valid way to group an array nums by whether elements are positive or negative using group_by returning :positive or :negative?

Step 1: Understand grouping by condition

Step 2: Check each option's block return value

Final Answer:

Quick Check:

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