Thread-Safe Singleton

Thread-safe singleton pattern using NSLock for mutable shared state.

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Language: swift | Tags: singleton concurrency design-pattern thread-safe

final class AppConfiguration: @unchecked Sendable {
    static let shared = AppConfiguration()

    private let lock = NSLock()
    private var _apiBaseURL: URL
    private var _timeout: TimeInterval

    var apiBaseURL: URL {
        lock.withLock { _apiBaseURL }
    }

    var timeout: TimeInterval {
        lock.withLock { _timeout }
    }

    private init() {
        _apiBaseURL = URL(string: "https://api.example.com")!
        _timeout = 30
    }

    func configure(apiBaseURL: URL, timeout: TimeInterval) {
        lock.withLock {
            _apiBaseURL = apiBaseURL
            _timeout = timeout
        }
    }
}

// Usage:
// AppConfiguration.shared.configure(apiBaseURL: url, timeout: 60)
// let baseURL = AppConfiguration.shared.apiBaseURL

Thread-Safe Singleton

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