HashMap Entry API for Key Management

Snippet

HashMap Entry API for Key Management

The Entry API provides ergonomic key insertion with fallbacks. or_insert inserts the value if the key is absent, otherwise leaves the existing value untouched. This pattern avoids redundant lookups common with get followed by insert.

snippet.rs

rust

use std::collections::HashMap;
 
fn main() {
    let mut scores = HashMap::new();
    scores.insert(String::from("Red"), 50);
 
    scores.entry(String::from("Blue")).or_insert(100);
    scores.entry(String::from("Red")).or_insert(100);
 
    println!("{:?}", scores);
}

Breakdown

scores.entry(String::from("Blue")).or_insert(100);

Entry for "Blue" doesn't exist, so inserts value 100

scores.entry(String::from("Red")).or_insert(100);

Entry for "Red" already exists, so leaves current value 50

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HashMap Entry API for Key Management

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