158 lines
3.6 KiB
Markdown
158 lines
3.6 KiB
Markdown
---
|
|
id: maps-records
|
|
title: Maps, Records
|
|
---
|
|
|
|
So far we've seen pretty basic data types. LIGO also offers more complex built-in constructs, such as Maps and Records.
|
|
|
|
## Maps
|
|
|
|
Maps are natively available in Michelson, and LIGO builds on top of them. A requirement for a Map is that its keys be of the same type, and that type must be comparable.
|
|
|
|
Here's how a custom map type is defined:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
type ledger is map(address, tez);
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
```cameligo
|
|
type ledger = (address, tez) map
|
|
```
|
|
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
And here's how a map value is populated:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
|
|
```pascaligo
|
|
const ledger: ledger = map
|
|
("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address) -> 1000mutez;
|
|
("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) -> 2000mutez;
|
|
end
|
|
```
|
|
> Notice the `->` between the key and its value and `;` to separate individual map entries.
|
|
>
|
|
> `("<string value>": address)` means that we type-cast a string into an address.
|
|
|
|
<!--Cameligo-->
|
|
|
|
```cameligo
|
|
let ledger: ledger = Map.literal
|
|
[ (("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address), 1000mutez) ;
|
|
(("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), 2000mutez) ;
|
|
]
|
|
```
|
|
> Map.literal constructs the map from a list of key-value pair tuples, `(<key>, <value>)`.
|
|
> Note also the `;` to separate individual map entries.
|
|
>
|
|
> `("<string value>": address)` means that we type-cast a string into an address.
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
### Accessing map values by key
|
|
|
|
If we want to access a balance from our ledger above, we can use the `[]` operator/accessor to read the associated `tez` value. However, the value we'll get will be wrapped as an optional; in our case `option(tez)`. Here's an example:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
const balance: option(tez) = ledger[("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address)];
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
|
|
```cameligo
|
|
let balance: tez option = Map.find_opt ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) ledger
|
|
```
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
#### Obtaining a map value forcefully
|
|
|
|
Accessing a value in a map yields an option, however you can also get the value directly:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
const balance: tez = get_force(("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), ledger);
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
|
|
```cameligo
|
|
let balance: tez = Map.find ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) ledger
|
|
```
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
|
|
## Records
|
|
|
|
Records are a construct introduced in LIGO, and are not natively available in Michelson. The LIGO compiler translates records into Michelson `Pairs`.
|
|
|
|
Here's how a custom record type is defined:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
type user is record
|
|
id: nat;
|
|
is_admin: bool;
|
|
name: string;
|
|
end
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
```cameligo
|
|
type user = {
|
|
id: nat;
|
|
is_admin: bool;
|
|
name: string;
|
|
}
|
|
```
|
|
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
And here's how a record value is populated:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
const user: user = record
|
|
id = 1n;
|
|
is_admin = True;
|
|
name = "Alice";
|
|
end
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
```cameligo
|
|
let user: user = {
|
|
id = 1n;
|
|
is_admin = true;
|
|
name = "Alice";
|
|
}
|
|
```
|
|
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|
|
|
|
|
|
### Accessing record keys by name
|
|
|
|
If we want to obtain a value from a record for a given key, we can do the following:
|
|
|
|
<!--DOCUSAURUS_CODE_TABS-->
|
|
<!--Pascaligo-->
|
|
```pascaligo
|
|
const is_admin: bool = user.is_admin;
|
|
```
|
|
|
|
<!--Cameligo-->
|
|
```cameligo
|
|
let is_admin: bool = user.is_admin
|
|
```
|
|
|
|
<!--END_DOCUSAURUS_CODE_TABS-->
|