rust crud example with vector

struct DataStore {
    store: Vec<(String, String)>,
}

impl DataStore {
    fn new() -> DataStore {
        DataStore { store: Vec::new() }
    }

    fn create(&mut self, key: String, value: String) {
        self.store.push((key, value));
    }

    fn read(&self, key: &str) -> Option<&String> {
        for (k, v) in &self.store {
            if k == key {
                return Some(v);
            }
        }
        None
    }

    fn update(&mut self, key: &str, value: String) {
        for (k, v) in &mut self.store {
            if k == key {
                *v = value;
            }
        }
    }

    fn delete(&mut self, key: &str) {
        self.store.retain(|(k, _)| k != key);
    }
}

fn main() {
    let mut data_store = DataStore::new();

    // Create a new entry
    data_store.create(String::from("key"), String::from("value"));

    // Read an entry
    let value = data_store.read("key");
    println!("{:?}", value);

    // Update an entry
    data_store.update("key", String::from("new value"));

    // Delete an entry
    data_store.delete("key");
}

This example defines a DataStore struct that contains a Vec field to store the key-value pairs. The create, read, update, and delete methods provide the necessary functionality for implementing CRUD operations.

Note that the read method returns an Option<&String>, which allows you to handle the case where the key is not found in the store. The update and delete methods take &str arguments instead of Strings to avoid moving the key value out of the store.