Type 'String' does not conform to protocol 'Sequence'

Question

If I want to print every characters in a string, I can use following code:

let flowers = "Flowers 💐"
for c in flowers.characters {
print(c)
}

But recently, when I used the following code from apple's API Link of API and got an error(which said: Type 'String' does not conform to protocol 'Sequence'), is api wrong or there something else I ignored?

Answer 1

let flowers = "Flowers 💐"
for c in flowers.characters {
    print(c)
}

is valid.