Rust - How to get Keys and Values from HashMap

Last Updated on February 22, 2020

In Rust, we can extract the keys and values from a HashMap using the iter() and keys() / get() / unwrap() functions.

Contents

1 Test Data
2 Using iter()
- 2.1 Output 1
- 2.2 Output 2
3 Using keys()
- 3.1 Output 1
- 3.2 Output 2

Test Data

let my_map:HashMap<i32, String> = HashMap::new();

my_map.insert(1, "one".to_string());
my_map.insert(2, "two".to_string());
my_map.insert(3, "three".to_string());

let my_map:HashMap<i32, String> = HashMap::new();

my_map.insert(1, "one".to_string());

my_map.insert(2, "two".to_string());

my_map.insert(3, "three".to_string());

Using iter()

Note that iter() return all key-value pairs in arbitrary order.

for  (k, v) in my_map.iter() {
    println!("key={}, value={}", k, v);
}

for (k, v) in my_map.iter() {

println!("key={}, value={}", k, v);

}

Output 1

key: 1 | value: one
key: 3 | value: three
key: 2 | value: two

key: 1 | value: one

key: 3 | value: three

key: 2 | value: two

Output 2

key: 2 | value: two
key: 1 | value: one
key: 3 | value: three

key: 2 | value: two

key: 1 | value: one

key: 3 | value: three

Using keys()

Note that keys() also return keys in arbitrary order.

for x in my_map.keys() {
    println!("{}", x);
    println!("{}", my_map.get(x).unwrap());
}

for x in my_map.keys() {

println!("{}", x);

println!("{}", my_map.get(x).unwrap());

}

Output 1

1
one
3
three
2
two

one

three

two

Output 2

3
three
1
one
2
two

three

one

two

Rust – How to get Keys and Values from HashMap

Test Data

Using iter()

Output 1

Output 2

Using keys()

Output 1

Output 2

Karl San Gabriel

Test Data

Using iter()

Output 1

Output 2

Using keys()

Output 1

Output 2

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Karl San Gabriel