[Solved] Why does the following code delete all occurrences of digits instead of leaving the string unchanged? str = "a1b2c3" str.gsub(/\d/) { |match| match if str.count("0-9") == 1 } | Ruby

Ruby - Regular Expressions

Why does the following code delete all occurrences of digits instead of leaving the string unchanged?

str = "a1b2c3"
str.gsub(/\d/) { |match| match if str.count("0-9") == 1 }

ABecause the block returns nil for all digits, so all digits are replaced with empty string

BBecause gsub replaces only last match by default

CBecause regex /\d/ matches only last digit

DBecause block syntax is invalid and causes error

Step-by-Step Solution

Solution:

Step 1: Understand block behavior in gsub
The block returns the replacement only if the count of digits is 1, else returns nil.
Step 2: Analyze digit count during iteration
Since str.count("0-9") is always 3, the block returns nil for all matches.
Final Answer:
Because the block returns nil for all digits, so all digits are replaced with empty string -> Option A
Quick Check:
Block return nil = empty replacement [OK]

Quick Trick: Block return nil replaces with empty string in gsub [OK]

Common Mistakes:

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Why does the following code delete all occurrences of digits instead of leaving the string unchanged?