CODEWITHSUNDEEP
stringswiftiteratorgenerator
Livioso
Livioso

Reputation: 1252

Swift Generators: What is the counterpart to next()?

I am currently learning Swift. While playing around with Generators I came across the following problem: Given a generator iter. How do I go back one item?

For example:

var str = "Hello World"
var iter = str.characters.generate()

iter.next() // => H
...
iter.next() // => l
iter.next() // => o


// how can I get this functionality to go back? 
iter.previous() => l
iter.next() => o

If not using generators: How can I get this behaviour to go forward and backward (in a String)?

Thanks in advance!

Upvotes: 1

Views: 129

Answers (1)

Cosyn
Cosyn

Reputation: 4997

Use index:

var str = "Hello World"

let i0 = str.startIndex
let i1 = i0.successor()
let i00 = i1.predecessor()

str[i0] // H
str[i1] // e
str[i00] // H

Upvotes: 2

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