Struct TransactionHelper

pub struct TransactionHelper<T, F> { /* private fields */ }

Helper for working with the new transasction interface.

This helper serves two purposes: to present a FnOnce interface for transactions, and to allow the extraction of data from within transactions.

Extracting Data

The CoreCryptoCommand interface requires some kind of interior mutability to extract any data: it takes an immutable reference to the implementing item, and returns the unit struct in the success case.

That pattern is relatively arcane and verbose, particularly when we just want to smuggle out some data from within the transaction. This helper is intended to ease and automate that process.

Use it like this (pseudocode):

// an extractor is always `Arc`-wrapped
let extractor: Arc<_> = TransactionHelper::new(move |context| async move {
    // return whatever you need from the transaction here
});
core_crypto.transaction(extractor.clone()).await?;
let return_value = extractor.into_return_value();

Panics

TransactionHelper is a one-shot item. Attempting to use the same extractor in two different transactions will cause a panic.

Implementations

impl<T, F, Fut> TransactionHelper<T, F>

where F: FnOnce(Arc<CoreCryptoContext>) -> Fut + Send + Sync, Fut: Future<Output = Result<T, CoreCryptoError>> + Send, T: Send + Sync,

pub fn new(func: F) -> Arc<Self>

pub fn into_return_value(self: Arc<Self>) -> T

Get the return value from the internal function.

Panics

• If there exists more than one strong reference to this extractor
• If the inner function was never called
• If the inner function returned an Err variant

In general if you call this after a call like

core_crypto.transaction(extractor.clone())?;

then this will be fine.

pub fn try_into_return_value(self: Arc<Self>) -> Option<T>

Safely get the return value from the internal function.

If there exists more than one strong reference to this item, or the inner function was never called or returned an Err variant, this will return None.

Trait Implementations

impl<T, F, Fut> CoreCryptoCommand for TransactionHelper<T, F>

where F: FnOnce(Arc<CoreCryptoContext>) -> Fut + Send + Sync, Fut: Future<Output = Result<T, CoreCryptoError>> + Send, T: Send + Sync,

fn execute<'life0, 'async_trait>( &'life0 self, context: Arc<CoreCryptoContext>, ) -> Pin<Box<dyn Future<Output = Result<(), CoreCryptoError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Will be called inside a transaction in CoreCrypto