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12: Adding and searching simple records

Overview

In this guide, you are going to write a dapp that provides a few basic functions to add and retrieve simple profile records that consist of a name, description, and an array of keywords.

This program supports the following functions:

  • The update function enables you to add a profile that consists of a name, a description, and keywords.

  • The getSelf function returns the profile for the principal associated with the function caller.

  • The get function performs a simple query to return the profile matching the name value passed to it. For this function, the name specified must match the name field exactly to return the record.

  • The search function performs a more complex query to return the profile matching all or part of the text specified in any profile field. For example, the search function can return a profile containing a specific keyword or that matches only part of a name or description.

This guide provides a simple example of how you can use the Rust CDK interfaces and macros to simplify writing dapps in Rust for the Internet Computer.

This guide demonstrates:

  • How to represent slightly more complex data—in the form of a profile as a record and an array of keywords—using the Candid interface description language.
  • How to write a simple search function with partial string matching.
  • How profiles are associated with a specific principal.

Prerequisites

Before getting started, assure you have set up your developer environment according to the instructions in the developer environment guide.

Creating a new project

Open a terminal window on your local computer, if you don’t already have one open. Then, create a new project by running the following command:

Use dfx new <project_name> to create a new project:

dfx new rust_profile

You will be prompted to select a language that your backend canister will use. Select 'Rust':

? Select a backend language: ›  
Motoko
❯ Rust
TypeScript (Azle)
Python (Kybra)

Then, select a frontend framework for your frontend canister, or select 'No frontend canister':

  ? Select a frontend framework: ›  
❯ SvelteKit
React
Vue
Vanilla JS
No JS template
No frontend canister

Lastly, you can include extra features to be added to your project:

  ? Add extra features (space to select, enter to confirm) ›
⬚ Internet Identity
⬚ Bitcoin (Regtest)
⬚ Frontend tests
dfx new --type=rust rust_profile

Then, navigate into your project directory by running the command:

cd rust_profile

Now that you have the files in place for your Rust dapp, you can replace the template lib.rs dapp with the Rust dapp you want to deploy on the Internet Computer.

To replace the default program, open the src/rust_profile_backend/Cargo.toml file in a text editor and add serde to dependencies.

[dependencies]
candid = "0.8.2"
ic-cdk = "0.6.0"
serde = "1.0"

Then, open the template src/rust_profile_backend/src/lib.rs file in a text editor and delete the existing content.

The next step is to add a Rust program that implements the getSelf, update, get, and search functions. To do this, copy and paste this code into the src/rust_profile_backend/src/lib.rs file.

use ic_cdk::{
export::{
candid::{CandidType, Deserialize},
Principal,
},
query, update,
};
use std::cell::RefCell;
use std::collections::BTreeMap;

type IdStore = BTreeMap<String, Principal>;
type ProfileStore = BTreeMap<Principal, Profile>;

#[derive(Clone, Debug, Default, CandidType, Deserialize)]
struct Profile {
pub name: String,
pub description: String,
pub keywords: Vec<String>,
}

thread_local! {
static PROFILE_STORE: RefCell<ProfileStore> = RefCell::default();
static ID_STORE: RefCell<IdStore> = RefCell::default();
}

#[query(name = "getSelf")]
fn get_self() -> Profile {
let id = ic_cdk::api::caller();
PROFILE_STORE.with(|profile_store| {
profile_store
.borrow()
.get(&id)
.cloned().unwrap_or_default()
})
}

#[query]
fn get(name: String) -> Profile {
ID_STORE.with(|id_store| {
PROFILE_STORE.with(|profile_store| {
id_store
.borrow()
.get(&name)
.and_then(|id| profile_store.borrow().get(id).cloned()).unwrap_or_default()
})
})
}

#[update]
fn update(profile: Profile) {
let principal_id = ic_cdk::api::caller();
ID_STORE.with(|id_store| {
id_store
.borrow_mut()
.insert(profile.name.clone(), principal_id);
});
PROFILE_STORE.with(|profile_store| {
profile_store.borrow_mut().insert(principal_id, profile);
});
}

Save your changes and close the file to continue.

Update the interface description file

Candid is an interface description language (IDL) for interacting with canisters running on the Internet Computer. Candid files provide a language-independent description of a canister’s interfaces including the names, parameters, and result formats and data types for each function a canister defines.

By adding Candid files to your project, you can ensure that data is properly converted from its definition in Rust to run safely on the Internet Computer blockchain.

To see details about the Candid interface description language syntax, see the Candid Guide or the Candid crate documentation.

To update Candid file for this guide open the src/rust_profile_backend/rust_profile_backend.did file in a text editor.

Copy and paste the following Profile type declaration and service definition for the getSelf, update, get, and search functions.

type Profile = record {
"name": text;
"description": text;
"keywords": vec text;
};

service : {
"getSelf": () -> (Profile) query;
"get": (text) -> (Profile) query;
"update": (Profile) -> ();
"search": (text) -> (opt Profile) query;
}

Save your changes and close the file to continue.

Start the local execution environment

Before you can build the rust_profile project, you need to connect to the local execution environment running in your development environment or the Internet Computer blockchain mainnet.

Start the local execution environment on your computer in the background by running the following command:

dfx start --background --clean

Depending on your platform and local security settings, you might see a warning displayed. If you are prompted to allow or deny incoming network connections, click Allow.

Register, build, and deploy your project

After you connect to the local execution environment running in your development environment, you can register, build, and deploy your project locally.

To do this, run the following command:

dfx deploy

Call functions on the deployed canister

After successfully deploying the canister, you can test the canister by calling the functions it provides.

For this guide:

  • Call the update function to add a profile.

  • Call the getSelf function to display the profile for the principal identity.

  • Call the search function to look up the profile using a keyword.

Updating records

Call the update function to create a profile record by running the following command:

dfx canister call rust_profile_backend update '(record {name = "Luxi"; description = "mountain dog"; keywords = vec {"scars"; "toast"}})'

In its current form, the dapp only stores and returns one profile. If you run the following command to add a second profile using the update function, the command replaces the Luxi profile with the Dupree profile:

dfx canister call rust_profile_backend update '(record {name = "Dupree"; description = "black dog"; keywords = vec {"funny tail"; "white nose"}})'

You can use the get, getSelf, and search functions, but they will only return results for the Dupree profile.

Retrieving records

Call the getSelf function to retrieve a profile record by running the following command:

dfx canister call rust_profile_backend getSelf

The command returns the profile you used the update function to add. For example:

(
record {
name = "Luxi";
description = "mountain dog";
keywords = vec { "scars"; "toast" };
},
)

Searching records

Run the following command to call the search function:

dfx canister call rust_profile_backend search '("black")'

This command finds the matching profile using the description and returns the profile:

(
opt record {
name = "Dupree";
description = "black dog";
keywords = vec { "funny tail"; "white nose" };
},
)

Adding profiles for new identities

In its current form, the dapp only stores one profile—the one associated with the principal invoking the commands. To test that the get, getSelf, and search functions do what you want them to, you need to add some new identities that can have different profiles.

To add identities for testing, first create a new user identity by running the following command, enter a passphrase to secure the identity when prompted:

dfx identity new Miles

The following output will be returned:

Your seed phrase for identity 'Miles': recycle  ...
This can be used to reconstruct your key in case of emergency, so write it down in a safe place.
Created identity: "Miles".

Call the update function to add a profile for the new identity. Enter your passphrase when prompted.

dfx --identity Miles canister call rust_profile_backend update '(record {name = "Miles"; description = "Great Dane"; keywords = vec {"Boston"; "mantle"; "three-legged"}})'

Call the getSelf function to view the profile associated with the default user identity.

dfx canister call rust_profile_backend getSelf

The command displays the profile currently associated with the default identity, in this example, the Dupree profile:

(
record {
name = "Dupree";
description = "black dog";
keywords = vec { "funny tail"; "white nose" };
},
)

Call the getSelf function using the Miles user identity by running the following command:

dfx --identity Miles canister call rust_profile_backend getSelf

The command displays the profile currently associated with the Miles identity, in this example:

(
record {
name = "Miles";
description = "Great Dane";
keywords = vec { "Boston"; "mantle"; "three-legged" };
},
)

Call the search function using part of the description or a keyword to further test the whether the correct profile is returned.

For example, to verify the Miles profile is returned, you might run the following command:

dfx canister call rust_profile_backend search '("Great")'

The command returns the Miles profile:

(
opt record {
name = "Miles";
description = "Great Dane";
keywords = vec { "Boston"; "mantle"; "three-legged" };
},
)

Call the search function to further test the whether the correct profile is returned.

For example, to verify the Dupree profile is returned, you might run the following command:

dfx canister call rust_profile_backend search '("black")'

The command returns the Dupree profile:

(
opt record {
name = "Dupree";
description = "black dog";
keywords = vec { "funny tail"; "white nose" };
},
)

Next steps

Next, you'll cover access control in Rust canisters.