To store a value through Casper Smart Contracts, we need to to defined a unforgeable reference (uref) for the value.
For example, for a contract that expects a single runtime argument named "message", we can declare this value in a constant and save it by using storage::new_uref.
<div class="remark-highlight"><pre class="language-rust"><code class="language-rust">use casper_contract::{
 contract_api::{runtime, storage}
};

const ARG_NAME: &#x26;str = "message";
let value: String = runtime::get_named_arg(ARG_NAME);
let value_ref = storage::new_uref(value);
</code></pre></div>
Next, we need to wrap the reference in a key, by using the .into() method.
Also, to save the value, we make can use the runtime::put_key method and pass the key.
<div class="remark-highlight"><pre class="language-rust"><code class="language-rust">const KEY_NAME: &#x26;str = "my_key";
let value_key: Key = value_ref.into();
runtime::put_key(KEY_NAME, value_key);
</code></pre></div>
Casper comes with a rich type system. Therefore, we can use the URef and Key types.
To use the String type from rust, we need to use alloc, since the we're into a no_str environment.
<div class="remark-highlight"><pre class="language-rust"><code class="language-rust">extern crate alloc;
use alloc::string::String;

use casper_types::{Key, URef};

let value_ref: URef = storage::new_uref(value);
let value_key: Key = value_ref.into();
</code></pre></div>
Check a basic storage contract setup from the
<a href="https://docs.casperlabs.io/dapp-dev-guide/writing-contracts/rust/#storage" target="_blank" rel="noopener noreferrer">official documentation</a>.
<h2>Challenge</h2>
Complete the program to store a value on the blockchain.
The key should have the following name: "casper_dapp".