0ec2b05070
This commit introduces a new interface that makes it easier and safer to handle unowned NostrDB notes, by leveraging new non-copyable and borrow features from modern Swift. Changelog-None Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
79 lines
2.5 KiB
Swift
79 lines
2.5 KiB
Swift
//
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// UnownedNdbNote.swift
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// damus
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//
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// Created by Daniel D’Aquino on 2025-03-25.
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//
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/// A function that allows an unowned NdbNote to be lent out temporarily
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///
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/// Use this to provide access to NostrDB unowned notes in a way that has much better compile-time safety guarantees.
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///
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/// # Usage examples
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///
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/// ## Lending out or providing Ndb notes
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///
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/// ```swift
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/// // Define the lender
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/// let lender: NdbNoteLender = { lend in
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/// guard let ndbNoteTxn = ndb.lookup_note(noteId) else { // Note: Must have access to `Ndb`
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/// throw NdbNoteLenderError.errorLoadingNote // Throw errors if loading fails
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/// }
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/// guard let unownedNote = UnownedNdbNote(ndbNoteTxn) else {
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/// throw NdbNoteLenderError.errorLoadingNote
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/// }
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/// lend(unownedNote) // Lend out the Unowned Ndb note
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/// }
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/// return lender // Return or pass the lender to another class
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/// ```
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///
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/// ## Borrowing Ndb notes
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///
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/// Assuming you are given a lender, here is how you can use it:
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///
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/// ```swift
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/// let borrow: NdbNoteLender = functionThatProvidesALender()
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/// try? borrow { note in // You can optionally handle errors if borrowing fails
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/// self.date = note.createdAt // You can do things with the note without copying it over
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/// // self.note = note // Not allowed by the compiler
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/// self.note = note.toOwned() // You can copy the note if needed
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/// }
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/// ```
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typealias NdbNoteLender = ((_: borrowing UnownedNdbNote) -> Void) throws -> Void
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enum NdbNoteLenderError: Error {
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case errorLoadingNote
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}
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/// A wrapper to NdbNote that allows unowned NdbNotes to be safely handled
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struct UnownedNdbNote: ~Copyable {
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private let _ndbNote: NdbNote
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init(_ txn: NdbTxn<NdbNote>) {
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self._ndbNote = txn.unsafeUnownedValue
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}
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init?(_ txn: NdbTxn<NdbNote?>) {
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guard let note = txn.unsafeUnownedValue else { return nil }
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self._ndbNote = note
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}
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init(_ ndbNote: NdbNote) {
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self._ndbNote = ndbNote
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}
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var kind: UInt32 { _ndbNote.kind }
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var known_kind: NostrKind? { _ndbNote.known_kind }
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var content: String { _ndbNote.content }
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var tags: TagsSequence { _ndbNote.tags }
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var pubkey: Pubkey { _ndbNote.pubkey }
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var createdAt: UInt32 { _ndbNote.created_at }
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var id: NoteId { _ndbNote.id }
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var sig: Signature { _ndbNote.sig }
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func toOwned() -> NdbNote {
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return _ndbNote.to_owned()
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}
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}
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