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Pourquoi le fait d'encapsuler os_log () empêche-t-il les doubles de se connecter correctement?

Prenons l'exemple suivant:

import Foundation
import os.log

class OSLogWrapper {

    func logDefault(_ message: StaticString, _ args: CVarArg...) {
        os_log(message, type: .default, args)
    }

    func testWrapper() {
        logDefault("WTF: %f", 1.2345)
    }
}

Si je crée une nouvelle instance de OSLogWrapper et appelle testWrapper()

let logger = OSLogWrapper()
logger.testWrapper()

Je reçois la sortie suivante dans la console Xcode:

2018-06-19 18:21:08.327979-0400 WrapperWTF[50240:548958] WTF: 0.000000

J'ai vérifié tout ce à quoi je pouvais penser et je ne pouvais pas comprendre ce qui n'allait pas ici. Regarder à travers la documentation ne donne rien d'utile.

Merci pour l'aide!

iosswiftlogging
23
Mike Akers

Comme mentionné dans mon commentaire à la réponse de Rob Mayoff ci-dessus, pour toute personne confrontée au même type de problème avec os_signpost(), voici un cours d'encapsulation que j'ai créé autour de ce problème:

import Foundation
import os
import _SwiftOSOverlayShims

public final class Signpost {

    private final let log: OSLog

    public init(log: OSLog) {
        self.log = log
    }

    public final func begin(name: StaticString, idObject: AnyObject? = nil) {
        if #available(iOS 12.0, *) {
            signpost(.begin, name: name, idObject: idObject)
        }
    }

    public final func begin(name: StaticString, idObject: AnyObject? = nil, _ format: StaticString, _ arguments: CVarArg...) {
        if #available(iOS 12.0, *) {
            signpost(.begin, name: name, idObject: idObject, format, arguments)
        }
    }

    public final func event(name: StaticString, idObject: AnyObject? = nil) {
        if #available(iOS 12.0, *) {
            signpost(.event, name: name, idObject: idObject)
        }
    }

    public final func event(name: StaticString, idObject: AnyObject? = nil, _ format: StaticString, _ arguments: CVarArg...) {
        if #available(iOS 12.0, *) {
            signpost(.event, name: name, idObject: idObject, format, arguments)
        }
    }

    public final func end(name: StaticString, idObject: AnyObject? = nil) {
        if #available(iOS 12.0, *) {
            signpost(.end, name: name)
        }
    }

    public final func end(name: StaticString, idObject: AnyObject? = nil, _ format: StaticString, _ arguments: CVarArg...) {
        if #available(iOS 12.0, *) {
            signpost(.end, name: name, idObject: idObject, format, arguments)
        }
    }

    @available(iOS 12.0, *)
    private final func signpost(_ type: OSSignpostType, name: StaticString, idObject: AnyObject? = nil) {
        guard log.signpostsEnabled else { return }
        let signpostID = getSignpostId(forObject: idObject)
        os_signpost(type, log: log, name: name, signpostID: signpostID)
    }

    @available(iOS 12.0, *)
    private final func signpost(
        _ type: OSSignpostType,
        dso: UnsafeRawPointer = #dsohandle,
        name: StaticString,
        idObject: AnyObject? = nil,
        _ format: StaticString,
        _ arguments: [CVarArg])
    {
        // This crazy mess is because [CVarArg] gets treated as a single CVarArg and repassing a CVarArg... actually passes a [CVarArg]
        // This was copied from the publicly available Swift source code at https://github.com/Apple/Swift/blob/master/stdlib/public/SDK/os/os_signpost.Swift#L40
        // THIS IS A HACK
        guard log.signpostsEnabled else { return }
        let signpostID = getSignpostId(forObject: idObject)
        guard signpostID != .invalid && signpostID != .null else { return }
        let ra = _Swift_os_log_return_address()
        name.withUTF8Buffer { (nameBuf: UnsafeBufferPointer<UInt8>) in
            // Since dladdr is in libc, it is safe to unsafeBitCast
            // the cstring argument type.
            nameBuf.baseAddress!.withMemoryRebound(to: CChar.self, capacity: nameBuf.count) { nameStr in
                format.withUTF8Buffer { (formatBuf: UnsafeBufferPointer<UInt8>) in
                    // Since dladdr is in libc, it is safe to unsafeBitCast
                    // the cstring argument type.
                    formatBuf.baseAddress!.withMemoryRebound(to: CChar.self, capacity: formatBuf.count) { formatStr in
                        withVaList(arguments) { valist in
                            _Swift_os_signpost_with_format(dso, ra, log, type, nameStr, signpostID.rawValue, formatStr, valist)
                        }
                    }
                }
            }
        }
    }

    @available(iOS 12.0, *)
    private final func getSignpostId(forObject idObject: AnyObject?) -> OSSignpostID {
        if let idObject = idObject {
            return OSSignpostID(log: log, object: idObject)
        }
        return .exclusive
    }
}
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