CODEWITHSUNDEEP
structrustiteratorclosuresmap-function
Ramon de Klein
Ramon de Klein

Reputation: 5706

Map a Vec of structures to another Vec of structure in Rust without cloning

I use a library that has the following structure:

struct KeyValue1 {
    key: Vec<u8>,
    value: Vec<u8>,
}

fn get() -> Vec<KeyValue1> { /* ... */ }

I need to convert this vector to an almost similar vector that has the following structure:

struct KeyValue2 {
    key: Vec<u8>,
    value: Vec<u8>,
}

To be able to convert from one vector to another, I currently use the following code:

let convertedItems = items.iter().map(|kv| -> KeyValue2{
  key: key.clone(),
  value: value.clone()
}).collect()

Although this works, it clones both vectors which is inefficient. I don't need the original items vector anymore, so I want to transfer ownership from KeyValue1 to KeyValue2, but I haven't found a way to do this.

Upvotes: 4

Views: 3670

Answers (1)

pretzelhammer
pretzelhammer

Reputation: 15155

Use into_iter() instead of iter() on the items vector if you don't need it after the conversion:

struct KeyValue1 {
    key: Vec<u8>,
    value: Vec<u8>,
}

struct KeyValue2 {
    key: Vec<u8>,
    value: Vec<u8>,
}

fn map_key_values(items: Vec<KeyValue1>) -> Vec<KeyValue2> {
    items
        .into_iter()
        .map(|kv| KeyValue2 {
            key: kv.key,
            value: kv.value,
        })
        .collect()
}

playground

Upvotes: 7

Related Questions