IterableLogUtil.formatDate() creates a new DateFormatter on every call, causing app hangs

[nicoleta-apetrei]

✍️ Issue Description

IterableLogUtil.formatDate() allocates a new DateFormatter instance on every invocation. DateFormatter (NSDateFormatter) is well-documented as expensive to create on iOS. When multiple SDK log calls fire in quick succession on the main thread (e.g. during foreground transitions), this causes fully-blocked app hangs of 2-3+ seconds.
Additionally, the expensive formatting happens before the log level is checked in the delegate, so even apps that set DefaultLogDelegate(minLogLevel: .error) pay the full cost for every ITBInfo() and ITBDebug() call internally.

Affected code

swift-sdk/Internal/Utilities/IterableLogUtil.swift, lines 52-56:

private static func formatDate(date: Date) -> String {
    let formatter = DateFormatter()          // ← new allocation every call
    formatter.dateFormat = "HH:mm:ss.SSSS"
    return formatter.string(from: date)
}

And the call site in log() at line 19-20:

func log(level: LogLevel, message: String?, file: String, method: String, line: Int) {
    let logMessage = IterableLogUtil.formatLogMessage(...)  // ← formats BEFORE delegate check
    logDelegate.log(level: level, message: logMessage)       // ← level filtered here, too late
}

Stack trace (from Sentry crash reporting)

-[NSDateFormatter stringForObjectValue:]
IterableLogUtil.formatDate (IterableLogUtil.swift)
IterableLogUtil.formatLogMessage (IterableLogUtil.swift)
  (×6 similar frames)
UIApplicationMain
main (main.swift)

App Hang Fully Blocked: 2.4–3.2 seconds. Occurs during foreground transition after returning from an external login flow.

Suggested fix

Two changes would resolve this:

1. Cache the DateFormatter as a static property:

private static let dateFormatter: DateFormatter = {
    let formatter = DateFormatter()
    formatter.dateFormat = "HH:mm:ss.SSSS"
    return formatter
}()

private static func formatDate(date: Date) -> String {
    dateFormatter.string(from: date)
}

2. Check the log level before formatting (optional but recommended):

Ideally the delegate protocol could be extended with a shouldLog(level:) method, or the level filtering could move into IterableLogUtil.log() itself before formatting. This would avoid the cost of formatLogMessage() entirely for filtered-out messages.

This issue was investigated with the help of Claude (Anthropic).

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👤 Iterable orgId: Wolt

📦 Iterable SDK version: 6.6.5 (also verified the code is unchanged in 6.6.7)

📲 iOS SDK version: From iOS 16 to iOS 26.x

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