Gsub with regex in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the gsub method do in Ruby?

The gsub method replaces all occurrences of a pattern in a string with a specified replacement.

beginner

How do you use a regular expression with gsub?

You pass a regular expression as the first argument to gsub, and it replaces all matches of that pattern in the string.

beginner

Example: What is the result of "hello123".gsub(/\d/, "*")?

It replaces all digits with '*', so the result is "hello***".

intermediate

Can gsub use a block with regex? What does it do?

Yes, gsub can take a block. For each match, the block runs and returns the replacement string.

beginner

What is the difference between sub and gsub?

sub replaces only the first match, while gsub replaces all matches in the string.

What does "abc123".gsub(/\d/, "#") return?

A "abc123"

B "abc###"

C "###123"

D "abc#23"

All digits (\d) are replaced by '#', so '123' becomes '###'.

Which method replaces only the first match in a string?

A gsub

B replace

C sub

D match

sub replaces only the first occurrence, gsub replaces all.

What does the regex /\w+/ match?

A One or more word characters (letters, digits, underscore)

B Only digits

C Whitespace characters

D Special characters

\w+ matches one or more word characters like letters, digits, or underscore.

How can you use a block with gsub?

A To convert string to uppercase

B To ignore matches

C To delete the string

D To specify a dynamic replacement for each match

The block runs for each match and returns the replacement string dynamically.

What will "hello world".gsub(/o/, '0') output?

A "hell0 w0rld"

B "hello world"

C "hell0 world"

D "0ell0 w0rld"

All 'o' characters are replaced with '0'.

Explain how to use gsub with a regular expression to replace all vowels in a string with '*'.

Think about the regex pattern for vowels and how gsub applies replacements.

Describe the difference between using sub and gsub when working with regex in Ruby.

Focus on how many replacements each method performs.