How to lookup from and insert into a HashMap in Rust?

The are multiple ways to check whether an element in a HashMap exist if not we insert it.

1) Using The entry API

use std::collections::hash_map::Entry;

let values: &Vec<isize> = match map.entry(key) {
    Entry::Occupied(o) => o.into_mut(),
    Entry::Vacant(v) => v.insert(default)
};

2) Using a briefer form

map.entry(key).or_insert_with(|| default)

Conclusion

In this page (written and validated by A. Gawali) you learned about How to lookup from and insert into a HashMap in Rust? . What's Next? If you are interested in completing Rust tutorial, we encourage you simply to start here: Rust Tutorial.

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