Trait for types that can be stored in Starknet contract storage. The Store trait enables types to be stored in and retrieved from Starknet’s contract storage. Cairo implements Store for most primitive types. However, collection types (arrays, dicts, etc.) do not implement Store directly. Instead, use specialized storage types, such as Vec or Map.

​
Signature

pub trait Store

​
Derivation

To make a type storable in contract storage, simply derive the Store trait: 
#[derive(Drop, starknet::Store)]
struct Sizes {
    tiny: u8,    // 8 bits
    small: u32,  // 32 bits
    medium: u64, // 64 bits
}
This allows the Size struct to be stored in a contract’s storage. There’s no real reason to implement this trait yourself, as it can be trivially derived. For efficiency purposes, consider manually implementing StorePacking to optimize storage usage.

​
Trait functions

​
read

Reads a value from storage at the given domain and base address.

​
Arguments

  • address_domain - The storage domain (currently only 0 is supported)
  • base - The base storage address to read from

​
Signature

fn read(address_domain: u32, base: StorageBaseAddress) -> Result>

​
write

Writes a value to storage at the given domain and base address.

​
Arguments

  • address_domain - The storage domain (currently only 0 is supported)
  • base - The base storage address to write to
  • value - The value to store

​
Signature

fn write(
    address_domain: u32, base: StorageBaseAddress, value: T,
) -> Result>

​
read_at_offset

Reads a value from storage at a base address plus an offset.

​
Arguments

  • address_domain - The storage domain (currently only 0 is supported)
  • base - The base storage address
  • offset - The offset from the base address where the value should be read

​
Signature

fn read_at_offset(
    address_domain: u32, base: StorageBaseAddress, offset: u8,
) -> Result>

​
write_at_offset

Writes a value to storage at a base address plus an offset.

​
Arguments

  • address_domain - The storage domain (currently only 0 is supported)
  • base - The base storage address
  • offset - The offset from the base address where the value should be written
  • value - The value to store

​
Signature

fn write_at_offset(
    address_domain: u32, base: StorageBaseAddress, offset: u8, value: T,
) -> Result>

​
size

Returns the size in storage for this type. This is bounded to 255, as the offset is a u8. As such, a single type can only take up to 255 slots in storage.

​
Signature

fn size() -> u8

​
scrub

Clears the storage area by writing zeroes to it.

​
Arguments

  • address_domain - The storage domain
  • base - The base storage address to start clearing
  • offset - The offset from the base address where clearing should start
The operation writes zeroes to storage starting from the specified base address and offset, and continues for the size of the type as determined by the size() function.

​
Signature

fn scrub(
    address_domain: u32, base: StorageBaseAddress, offset: u8,
) -> Result>