Iterator implementation on custom struct - problems - rust

Question

Im trying print out a encoded hex string of some basic data ive inserted as a lesson how to serialize/deserialize data. However todo this im having to implement an iterator for a Struct that has a single element of type Vec. Im getting the below error and don't understand why, I realize my code is incomplete in the next() implementation. I'm fairly new to iterators, any help would be appreciated.
Error:
error[E0599]: no method named `iter_mut` found for struct `MyData` in the current scope
--> src/main.rs:110:22
|
21 | pub(crate) struct MyData {
| ------------------------ method `iter_mut` not found for this struct
...
110 | for v in my_data.iter_mut() {
|
#[derive(Serialize, Deserialize, Debug)]
#[serde(transparent)]
struct MyHex {
#[serde(with = "hex::serde")]
hex: Vec<u8>,
}
#[derive(Serialize, Deserialize, Debug)]
pub(crate) struct MyData {
data: Vec<MyHex>,
}
impl Iterator for MyData {
type Item = usize;
fn next(&mut self) -> Option<Self::Item>;
}
fn main() -> Result<()> {
let data = "
{
\"data\": [\"bbac4013c1ca3482155b584d35dac185\",
\"a08898e81f1ddb6612aa12641b856aa9\",
\"bbac4013c1ca3482155b584d35dac185\"
]
}";
let my_data: MyData = serde_json::from_str(data)?;
for v in my_data.iter_mut() {
println!("{:?}", hex::encode(v));
}
return Ok(());
}

Answer 1

You question is a little fuzzy but let's try to see what we can do:
Iterating over inner field
If you want to do something with the data byte by byte, you can iterate over data itself:
for hex in my_data.data { ... }
Iterating without exposing inner fields
You can also return iterator over data without exposing the field to the rest of the code:
impl MyData {
fn iter_data(&self) -> impl Iterator<Item = &MyHex> {
self.data.iter()
}
}
...
for hex in my_data.iter_data() { ... }
Implementing IntoIterator
If you want MyData work as an iterator, you can implement IntoIterator trait for it:
impl<'a> IntoIterator for &'a MyData {
type Item = &'a MyHex;
type IntoIter = std::slice::Iter<'a, MyHex>;
fn into_iter(self) -> Self::IntoIter {
self.data.iter()
}
}
...
for v in &my_data {
println!("{:?}", v);
}
Playground
Implementing Iterator for MyData
To implement Iterator you need to provide the next method, which on every call will return the next item in the iterator while there are any items left. To do so you would add a field to you MyData that keeps track of the last item that was return, and increment that pointer on every call of next().
But from your code I guess this is not something you actually want. Go rather with one of the previous options.