Current-guide.md

Current Guide - how to use it in Babylon iOS Project

Where can I find it?

• Current is the global instance of the World type which is located in the BabylonDependencies.framework. Its purpose is to provide convenient access to the instances that should be shared between different parts of the app (cross-cutting concerns). For more information please read the How Control the World proposal.

Beyond the Proposal

All the properties in Current must have their initial values provided at initialisation time. But that's not the reality for all of them. These async properties have their initial value provided in the SharedAppDelegate through the method setupCurrent. Only after that, the whole world is ready to be used.

Dos and Don'ts

Do

• access Current only from topmost AppDelegate until Builders layer
• pass the required dependencies down the chain;
• create a customized version to fit your specific needs for tests and set it in the test setUp method. Please reset it on the tearDown method

override func setUp() {
    let utc = TimeZone(identifier: "UTC")!
    let locale = Locale(identifier: "en_GB")
    Current = World(autoupdatingTimeZone: utc, autoupdatingLocale: locale)
}

override func tearDown() {
    Current = .production // which returns a new `World()`
}

Don't

• access Current from any other layer other than Builder. All the other layers (ViewModel, FlowController, ViewController, Model, BusinessController) continue to receive their dependencies through injection when created by the builder, preferably at initialisation time;
• inject current as a dependency;
• mutate Current's properties – or re-affect it to another instance – after SharedAppDelegate.setupCurrent(). You are only allowed to mutate Current in tests, not in app. In Release configuration it's a constant let anyway to prevent mutation;

#if DEBUG
public var Current: World = .production
#else
public let Current: World = .production
#endif

Proposal reference: How Control the World