Injecting dependencies by value, scenario 1

conf_deps_by_value1.swift

import Foundation

// MARK: - (1) Original app blob scenario:

/// We have the app blob with original code. It contains a builder to build a UI component, which contains a UIView:
/// _Note: We use enums just for namespaces._
enum AppBlob {
    /// Some class that needs to be run on Main thread:
    struct UIView {
        init() {
            dispatchPrecondition(condition: .onQueue(.main))
        }
        func load() {
            // ...
        }
    }
    /// The builder:
    struct Builder {
        func build() {
            /// Do some work on a background thread, but UI-related stuff should be done on Main thread:
            DispatchQueue.main.sync {
                let view = UIView()
                view.load()
            }
        }
    }
}

/// Run:
do {
    /// Run code on a background thread to deload Main thread:
    DispatchQueue.global().async {
        /// Create a builder and run it:
        let builder = AppBlob.Builder()
        builder.build()
    }
}


// MARK: - (2) After modularization scenario:

/// Here we have modularized the constructor into some module. The only change is that we now use the configuration object to inject dependencies:

enum SomeModule {
    /// The configuration object to host injected dependencies:
    struct Configuration {
        let view: AppBlob.UIView
    }
    /// The builder moved to `SomeModule`:
    struct Builder {
        let cfg: Configuration
        func build() {
            /// Do some work on a background thread, but UI-related stuff should be done on Main thread:
            DispatchQueue.main.sync {
                cfg.view.load()
            }
        }
    }
}

/// Run:
do {
    /// Runs code on a background thread to deload Main thread:
    DispatchQueue.global().async {
        /// Create a configuration object to pass dependincies to the builder:
        let cfg = SomeModule.Configuration(view: AppBlob.UIView())
        /// Create a builder and run it:
        let builder = SomeModule.Builder(cfg: cfg)
        builder.build()
    }

}

// MARK: -

/// Give async code some time to complete before exiting the app:
RunLoop.current.run(until: .init(timeIntervalSinceNow: 5))