Using the .append() Method

To join two vectors, you can utilize the .append() method, which modifies the original vector directly. This method requires the second vector as an input, effectively merging its elements into the first vector. Here’s a practical example:

let mut vec1 = vec![1, 2, 3];

let mut vec2 = vec![4, 5, 6];

vec1.append(&mut vec2);

assert_eq!(vec1, [1, 2, 3, 4, 5, 6]);

assert_eq!(vec2, []);

Notice that .append() consumes the second vector (vec2), leaving it empty after the operation. You must pass vec2 as a mutable reference using &mut.

Using the .extend() Method

Alternatively, the .extend() method can be employed to concatenate vectors without altering the second vector. This method accepts an iterator as an argument, allowing for flexible concatenation. Here’s how it works:

let mut vec1 = vec![1, 2, 3];

let vec2 = vec![4, 5, 6];

vec1.extend(vec2);

assert_eq!(vec1, [1, 2, 3, 4, 5, 6]);

While .extend() does not modify the original vec2, it is important to note that it will not maintain the order of elements if an iterator is used that returns them differently. In this example, since vec2 is an ordinary vector, the order remains intact.

Using Iterators for Concatenation

To concatenate vectors without requiring a mutable reference on them, you can leverage the .into_iter() method. This approach allows you to create an iterator from one vector and pass it to the .extend() method of another vector, facilitating a clean concatenation without mutation. Here’s an illustration:

let vec1 = vec![1, 2, 3];

let vec2 = vec![4, 5, 6];

let mut vec3 = vec1;

vec3.extend(vec2.into_iter());

assert_eq!(vec3, [1, 2, 3, 4, 5, 6]);

In this scenario, vec2 is moved, rendering it unusable afterward. This technique effectively combines the vectors while adhering to Rust’s ownership rules.

Learn more about vectors in Rust with this video: "Rust Crash Course | #12 Vectors."

For a deeper dive, watch this video: "Rust: Vectors."

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