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Update Using enums in storage section #2832

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Jan 8, 2025
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Update Using enums in storage section #2832

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483733a
Update `Using enums in storage` section
franciszekjob Jan 8, 2025
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Update docs/src/snforge-advanced-features/storage-cheatcodes.md
franciszekjob Jan 8, 2025
b35269d
Update `Using enums in storage` section
franciszekjob Jan 8, 2025
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Update `Using enums in storage` section
franciszekjob Jan 8, 2025
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4 changes: 3 additions & 1 deletion docs/src/snforge-advanced-features/storage-cheatcodes.md
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Expand Up @@ -47,7 +47,9 @@ And perform a test checking `load` and `store` behavior in context of those stru

## Example: Using enums in storage

Normally, enums use 0-based layout. For example, `Option::Some(100)` will be serialized as `[0, 100]`. However, their storage layout is 1-based, so `Option::Some(100)` should be serialized as `[1, 100]`. It's because the first variant needs to be distinguished from an uninitialized storage slot.
Enums use 0-based layout for serialization. For example, `FirstVariantOfSomeEnum(100)` will be serialized as `[0, 100]`. However, their Starknet storage layout is 1-based for most enums, especially for these with derived `Store` trait implementation. Therefore, `FirstVariantOfSomeEnum(100)` will be stored on Starknet as `[1, 100]`.

Remember that this rule may not hold for enums that with manual `Store` trait implementation. The most notable example is `Option`, e.g. `Option::None` will be stored as `[0]` and `Option::Some(100)` will be stored as `[1, 100]`.

Below is an example of a contract which can store `Option<u256>` values:

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