Scan for all matches in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Ruby method String#scan do?

It searches the string for all occurrences that match a given pattern and returns them as an array.

beginner

How do you use scan to find all words in a string?

Use scan with a regular expression like /\w+/ to find all word sequences.

intermediate

What is the return type of scan when used with a pattern that has capture groups?

It returns an array of arrays, where each inner array contains the captured groups for each match.

intermediate

How can you use a block with scan?

You can pass a block to scan to process each match as it is found instead of collecting them in an array.

beginner

What happens if scan finds no matches?

It returns an empty array.

What does "hello123".scan(/\d+/) return?

A ["h", "e", "l", "l", "o"]

B ["hello"]

C []

D ["123"]

The pattern /\d+/ matches one or more digits, so it finds "123".

Which of these returns an array of arrays when using scan?

A Using a pattern without capture groups

B Using a pattern with capture groups

C Using <code>scan</code> with no arguments

D Using <code>scan</code> on an empty string

Capture groups cause scan to return arrays of the captured parts.

What does "abc123def".scan(/[a-z]+/) return?

A ["abc", "def"]

B ["abc123def"]

C ["123"]

D []

The pattern matches sequences of letters, so it finds "abc" and "def".

How can you process matches one by one with scan?

A By passing a block to <code>scan</code>

B By calling <code>each</code> on the string

C By using <code>match</code> instead

D By converting the string to an array first

Passing a block to scan lets you handle each match as it is found.

What does "no digits".scan(/\d+/) return?

A ["0"]

B ["no", "digits"]

C []

D nil

No digits are found, so scan returns an empty array.

Explain how the Ruby scan method works to find all matches in a string.

Think about how you find all parts of a text that fit a pattern.

Describe how you can use a block with scan and why it might be useful.

Consider what happens if you want to do something with each match immediately.