CODEWITHSUNDEEP
stringswift
SLN
SLN

Reputation: 5082

Why strings cannot be indexed by integer values

I learned that Swift strings cannot be indexed by integer values. I remembered it and I use the rule. But I've never fully understood the mechanic behind it.

The explanation of from the official document is as follows

"Different characters can require different amounts of memory to store, so in order to determine which Character is at a particular position, you must iterate over each Unicode scalar from the start or end of that String. For this reason, Swift strings cannot be indexed by integer values"

I've read it several times, I still don't quite get the point. Can someone explain me a bit more why Swift String cannot be indexed by integer values?

Many Thanks

Upvotes: 3

Views: 1314

Answers (1)

njzk2
njzk2

Reputation: 39406

A string is stored in memory as an array of bytes.

A given character can require 1 to 4 bytes for the basic codepoint, plus any number of combining diacritical mark.

For example, é requires 2 bytes.

Now, if you have the strings efgh and éfgh, to access the second character (f), for the first string, the character is in the byte array at index 1, for the second string, it is at index 2.

In order to know that, you need to inspect the first character. For accessing any character based on its index, you need to go through all the previous characters to know how many bytes each takes.

Upvotes: 1

Related Questions