Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Document Map #195

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension


Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions docs-test-gen/Cargo.lock

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

1 change: 1 addition & 0 deletions docs-test-gen/Cargo.toml
Original file line number Diff line number Diff line change
@@ -29,3 +29,4 @@ serde = "*"
cw-storey = "*"
schemars = "0.8.21" # Used in entrypoint example
thiserror = "1.0.65"
storey = "*"
234 changes: 234 additions & 0 deletions src/pages/storey/containers/map.mdx
Original file line number Diff line number Diff line change
@@ -5,3 +5,237 @@ tags: ["storey", "containers"]
import { Callout } from "nextra/components";

# Map

A `Map` is a container that maps keys to instances of another container.

Most commonly, you will use a `Map` to store a list of items. For example, the signature could be a
`Map<String, Item<String>>` to store a list of signatures for each user. (See the first example.)

## Examples

### Keeping balances

Let's say you want to keep track of the balances of each user. You can do this with a
`Map<String, Item<Uint128>>`.

```rust template="storage" showLineNumbers {6,8,10,12,14}
use cw_storey::containers::{Item, Map};
use cw_storey::CwStorage;

const BALANCES_IX: u8 = 0;

let balances: Map<String, Item<Uint128>> = Map::new(BALANCES_IX);
let mut cw_storage = CwStorage(&mut storage);
let mut access = balances.access(&mut cw_storage);

assert_eq!(access.entry("alice").get().unwrap(), None);

access.entry_mut("alice").set(&Uint128::new(1000)).unwrap();

assert_eq!(access.entry("alice").get().unwrap(), Some(Uint128::new(1000)));
```

- _line 6:_ Here we construct the `Map` facade. The constructor takes a key, which is the prefix of
the keys in the underlying storage backend.
- _line 8:_ The [`access`] method returns a [`MapAccess`] entity, which allows manipulating the map.
- _line 10:_ Here we try to access the balance of `alice`. Since she doesn't have one yet, it
returns `None`. The [`entry`] method returns an [`ItemAccess`] entity, which allows manipulating
the item stored under the key `alice`.
- _line 12:_ Here we set Alice's balance to `1000`.
- _line 14:_ We check that the balance is now `1000`.

#### Iterating over the balances

Iterating over the balances is pretty straightforward. The [`keys`] method returns an iterator over
the keys, the [`values`] method returns an iterator over the values, and the [`pairs`] method
returns an iterator over both.

```rust template="storage" showLineNumbers {4, 17, 19}
use cw_storey::containers::{Item, Map};
use cw_storey::CwStorage;

use storey::containers::IterableAccessor as _;

const BALANCES_IX: u8 = 1;

let balances: Map<String, Item<Uint128>> = Map::new(BALANCES_IX);
let mut cw_storage = CwStorage(&mut storage);
let mut access = balances.access(&mut cw_storage);

access.entry_mut("bob").set(&Uint128::new(500)).unwrap();
access.entry_mut("carol").set(&Uint128::new(1500)).unwrap();
access.entry_mut("dave").set(&Uint128::new(2000)).unwrap();

assert_eq!(
access.pairs().collect::<Result<Vec<_>, _>>().unwrap(),
vec![
(("bob".to_string(), ()), Uint128::new(500)),
(("carol".to_string(), ()), Uint128::new(1500)),
(("dave".to_string(), ()), Uint128::new(2000)),
]
);

assert_eq!(
access.keys().collect::<Result<Vec<_>, _>>().unwrap(),
vec![("bob".to_string(), ()), ("carol".to_string(), ()), ("dave".to_string(), ())]
);

assert_eq!(
access.values().collect::<Result<Vec<_>, _>>().unwrap(),
vec![Uint128::new(500), Uint128::new(1500), Uint128::new(2000)]
);
```

- _line 4:_ Here we import the [`IterableAccessor`] trait. This trait provides unbounded iteration.
- _line 17:_ The `pairs` method returns an iterator over the key-value pairs.
- _line 19:_ Notice the key type is `(String, ())`. This is likely to become just `String` in the
future. For now, consider this a quirk of the design. This will make more sense once you get to
composite maps.

#### Bounded iteration

Bounded iteration is also supported in many cases.

```rust template="storage" showLineNumbers {17}
use cw_storey::containers::{Item, Map};
use cw_storey::CwStorage;

use storey::containers::BoundedIterableAccessor as _;

const BALANCES_IX: u8 = 1;

let balances: Map<String, Item<Uint128>> = Map::new(BALANCES_IX);
let mut cw_storage = CwStorage(&mut storage);
let mut access = balances.access(&mut cw_storage);

access.entry_mut("bob").set(&Uint128::new(500)).unwrap();
access.entry_mut("carol").set(&Uint128::new(1500)).unwrap();
access.entry_mut("dave").set(&Uint128::new(2000)).unwrap();

assert_eq!(
access.bounded_pairs(Some("bob"), Some("dave")).collect::<Result<Vec<_>, _>>().unwrap(),
vec![(("bob".to_string(), ()), Uint128::new(500)), (("carol".to_string(), ()), Uint128::new(1500))]
);
```

Here we used the [`bounded_pairs`] method to iterate over some key-value pairs. Other bounded
methods are also available: [`bounded_keys`] and [`bounded_values`].

The bounds are provided as arguments to the methods. Currently, the bounds are inclusive on the
lower bound and exclusive on the upper bound. In a future release (soon!) this will be configurable.

### Keeping balances with composition

Alright, let's say this time you'd also like to keep track of the balances of each user, but each
can have multiple different tokens. This is where composition comes in.

```rust template="storage" showLineNumbers {6, 10-14}
use cw_storey::containers::{Item, Map};
use cw_storey::CwStorage;

const BALANCES_IX: u8 = 0;

let balances: Map<String, Map<String, Item<Uint128>>> = Map::new(BALANCES_IX);
let mut cw_storage = CwStorage(&mut storage);
let mut access = balances.access(&mut cw_storage);

access.entry_mut("alice").entry_mut("USDT").set(&Uint128::new(1000)).unwrap();
access.entry_mut("alice").entry_mut("OSMO").set(&Uint128::new(2000)).unwrap();

assert_eq!(access.entry("alice").entry("USDT").get().unwrap(), Some(Uint128::new(1000)));
assert_eq!(access.entry("alice").entry("OSMO").get().unwrap(), Some(Uint128::new(2000)));
```

This example is similar to the previous one, but this time we have an extra level of nesting.

First of all, our type is `Map<String, Map<String, Item<Uint128>>>`. The outer map maps user
addresses to inner maps. The inner map maps token denominations to actual balances.

When we access the stuff, the first [`entry`]/[`entry_mut`] call accesses a record in the outer map,
and the second one accesses a record in the inner map.

<Callout>
In [`cw-storage-plus`], you can achieve the same
effect using composite keys (tuples). The example above would then use something like
`cw_storage_plus::Map<(String, String), Uint128>`.
</Callout>

#### Iterating over the balances

Let's take a look at what iteration looks like with a composite map.

```rust template="storage" showLineNumbers {18, 27}
use cw_storey::containers::{Item, Map};
use cw_storey::CwStorage;
use cosmwasm_std::Order;

use storey::containers::IterableAccessor as _;

const BALANCES_IX: u8 = 1;

let balances: Map<String, Map<String, Item<u64>>> = Map::new(BALANCES_IX);
let mut cw_storage = CwStorage(&mut storage);
let mut access = balances.access(&mut cw_storage);

access.entry_mut("alice").entry_mut("USDT").set(&1000).unwrap();
access.entry_mut("alice").entry_mut("OSMO").set(&2000).unwrap();
access.entry_mut("bob").entry_mut("USDT").set(&1500).unwrap();

assert_eq!(
access.pairs().collect::<Result<Vec<_>, _>>().unwrap(),
vec![
(("bob".into(), ("USDT".into(), ())), 1500),
(("alice".into(), ("OSMO".into(), ())), 2000),
(("alice".into(), ("USDT".into(), ())), 1000),
]
);

assert_eq!(
access.entry("alice").pairs().collect::<Result<Vec<_>, _>>().unwrap(),
vec![(("OSMO".into(), ()), 2000), (("USDT".into(), ()), 1000)]
);
```

Here we iterated twice, but each time we got a different view of the data. Each iteration was at a
different level.

- _line 18:_ We call `pairs` on the outer map, which gives us all the entries.
- _line 27:_ We call `pairs` on the inner map under the key `alice`, which gives us all of Alice's
balances.

We can of course do the same with the `keys` and `values` methods.

<Callout type="warning">
When iterating over the entries in a `Map` using the `pairs`, `keys`, and `values` methods, the
**order of the keys is not guaranteed to be sensible** (though it is deterministic). If you need a
sensible order, try using the bounded iterators. If they do not exist (`BoundedIterableAccessor` is not implemented for the accessor), sensibly ordered iteration is not
possible.

Bounded or sensibly ordered iteration is not possible when both of the following conditions are met:

- The key is dynamically sized (e.g. `String`, `Vec<u8>`, etc.).
- The value type is a collection (`Map`, `Column`, etc.) rather than something like `Item`.

This is why, in the example above, bounded iteration (and a sensible order) is only possible for the
inner map.

</Callout>

[`cw-storage-plus`]: /cw-storage-plus/containers/map
[`bounded_pairs`]:
https://docs.rs/storey/latest/storey/containers/trait.BoundedIterableAccessor.html#method.bounded_pairs
[`bounded_keys`]:
https://docs.rs/storey/latest/storey/containers/trait.BoundedIterableAccessor.html#method.bounded_keys
[`bounded_values`]:
https://docs.rs/storey/latest/storey/containers/trait.BoundedIterableAccessor.html#method.bounded_values
[`access`]: https://docs.rs/storey/latest/storey/containers/map/struct.Map.html#method.access
[`entry`]: https://docs.rs/storey/latest/storey/containers/map/struct.MapAccess.html#method.entry
[`entry_mut`]:
https://docs.rs/storey/latest/storey/containers/map/struct.MapAccess.html#method.entry_mut
[`keys`]: https://docs.rs/storey/latest/storey/containers/trait.IterableAccessor.html#method.keys
[`values`]:
https://docs.rs/storey/latest/storey/containers/trait.IterableAccessor.html#method.values
[`pairs`]: https://docs.rs/storey/latest/storey/containers/trait.IterableAccessor.html#method.pairs
[`ItemAccess`]: https://docs.rs/storey/latest/storey/containers/struct.ItemAccess.html
[`MapAccess`]: https://docs.rs/storey/latest/storey/containers/map/struct.MapAccess.html
[`IterableAccessor`]: https://docs.rs/storey/latest/storey/containers/trait.IterableAccessor.html