v0.2.6-alpha.3

Swift: Resolve a download

resolveDownload(_:) answers the local path of an attachment's bytes. When the file is already in the sandbox it returns at once; when it is not, and a transfer is configured, it fetches the object once and then answers the fresh path.

Examples#

Basic#

// TodoApp/AttachmentView.swift (excerpt)
import Foundation
import KizunaSync

if let path = try await kizunasync.resolveDownload(reference) {
  imageURL = URL(fileURLWithPath: path)
}

From a row a peer wrote#

// TodoApp/AttachmentView.swift (excerpt)
import KizunaSync

let raw = try await kizunasync.query(
  table: "todos",
  plan: KizunaSyncQuery.single(filters: [KizunaSyncQuery.eq("id", todoId)])
)
guard let row = raw as? [String: Any], let reference = row["image_path"] as? String else { return }
let path = try await kizunasync.resolveDownload(reference)

Parameters#

Name	Type	Required	Description
`reference`	`String`	Yes	The value stored in the row's attachment column, as Attach a file produced it on the device that added the file.

Returns#

String?. The sandbox path of the bytes, or nil when the reference has no queue row on this device, when no transfer is configured, when the queue row is mid-transfer, orphaned, or evicted, when the store is soft-blocked, or when the fetch did not produce a file.

Errors#

Code	Condition
`ATTACHMENT_PORTS_MISSING`	A download had to run and the client was created without `attachmentRoot`.
`STORE`, `JSON`	The attachment queue could not be read or updated.
`ENGINE_UNAVAILABLE`	The client has no engine because Initializing has not run.

Notes#

The call is the lazy half of the attachment queue: a reference a pull delivered is registered as queued and nothing is fetched until something asks for it, so a list of 500 rows does not download 500 files. A row whose sandbox file disappeared, after an operating-system purge or a cleared cache, is re-fetched by the same path rather than answering nil forever.

A transfer failure is recorded on the queue row rather than thrown: the call answers nil and Get attachment status carries failed with the message. A download with no known SHA-256, neither the server's nor one this device kept, fails the same way, with errorCode ATTACHMENT_UNVERIFIED, and fetches nothing; Retry an attachment or a later call tries again. Bytes not on Storage leave the row queued, the ordinary state while the writing device is uploading. Supabase documents the underlying object read and its failures under Storage error codes.

← Attach a file Get attachment status →

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