Implementing diferent iterators on same data structure

Question

I want to have the option to return 2 completely different complex orders from an iterator. (referring to complex as not only reversed and normal order)

What would be the best way to accomplish this, i could have a method that saves the state before hand like:

/*for simple order*/
data_struct_instance.select_iter(data_struct_order::Simple);
let iter_simple = data_struct_instance.iter();

/*for complex order 1*/
data_struct_instance.select_iter(data_struct_order::Complex1);
let iter_complex1 = data_struct_instance.iter();

But i would rather avoid the internal state generated by the method .select_iter() is there a better way to accomplish this.

E_net4 · Accepted Answer · 2023-05-31T17:02:18.970

Use different methods returning different kinds of iterators. It is a common pattern, even found in the core library (see e.g. str::chars and str::char_indices), and comes with the advantage of enabling different return types for iterators without trait objects.

A complete example based on your code is not possible, but the public interface could be made into something like this:

struct DataStruct {
   // ...
}

impl DataStruct {
    pub fn simple_iter(&self) -> impl Iterator<SimpleData> + '_ {
        todo!()
    }

    pub fn complex_iter(&self) -> impl Iterator<ComplexData> + '_ {
        todo!()
    }
}

Implementing diferent iterators on same data structure

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