Ruby: How to count the number of times a string appears in another string?

Question

I'm trying to count the number of times a string appears in another string.

I know you can count the number of times a letter appears in a string:

string = "aabbccddbb"
string.count('a')
=> 2

But if I search for how many times 'aa' appears in this string, I also get two.

string.count('aa')
=> 2

I don't understand this. I put the value in quotation marks, so I'm searching for the number of times the exact string appears, not just the letters.

Answer 1

It's because the count counts characters, not instances of strings. In this case 'aa' means the same thing as 'a', it's considered a set of characters to count.

To count the number of times aa appears in the string:

string = "aabbccddbb"
string.scan(/aa/).length
# => 1
string.scan(/bb/).length
# => 2
string.scan(/ff/).length
# => 0