你好！我叫Anton，我是Joom的iOS开发人员。在本文中，您将学习我们如何与Needle DI框架一起使用，以及它是否真的可以与类似的解决方案相提并论，是否可以在生产代码中使用。仅此而已-当然，还有性能评估。

背景

, iOS Objective-C, DI-, Typhoon. , Typhoon overhead runtime, .

Joom , , . , iOS- , .

Objective-C Swift, . ?

Swift, Objective-C DI. , : .

, runtime. property, :

• , ;
• ;
• .
  
  lazy property . , , runtime.

, compile time. - header implementation, - , .

, .

, DI- . 5-6 .

, :

• forward declaration .h- ;
• .h- ;
• #import header .m- ;
• .m- ;
• , .

, ? .

, C. copy/paste , .

. , , . .

. , . , SOLID, , , , . Objective-C.

, , 2018.

, « » , .

Swift Objective-C.

DI .

framework, , Objective-C. boilerplate .

DI framework- Swift. C Swinject Dip. .

:

• runtime. , , , .
• runtime, .
• , force unwrap ! (Swinject) try! (Dip) , .

, . , DI framework Needle.

Needle — open-source Uber, Swift 2018 ( — 7 2018).

compile time safety .

.

Needle : NeedleFoundation framework.

DI . SourceKit.

. DependencyProvider, . .

, - , , .

. :

1. homebrew:
   
   brew install needle
2. :
   
   git clone https://github.com/uber/needle.git & cd Generator/bin/needle

Run Script , , . :

export SOURCEKIT_LOGGING=0 && needle generate ../NeedleGenerated.swift

../NeedleGenerated.swift — , .

NeedleFoundation

NeedleFoundation — , .

. CocoaPods:

pod 'NeedleFoundation'

root-, BootstrapComponent.

Component.

DI- , Dependency generic type- .

:

protocol SomeUIDependency: Dependency {
    var applicationURLHandler: ApplicationURLHandler { get }
    var router: Router { get }
}

final class SomeUIComponent: Component<SomeDependency> {
    ...
}

, <EmptyDependency>.

DI- lazy- path name:

// Component.swift
public lazy var path: [String] = {
        let name = self.name
        return parent.path + ["\(name)"]
}()

private lazy var name: String = {
    let fullyQualifiedSelfName = String(describing: self)
    let parts = fullyQualifiedSelfName.components(separatedBy: ".")
    return parts.last ?? fullyQualifiedSelfName
}()

, DI- .

, :

RootComponent->UIComponent->SupportUIComponent,

SupportUIComponent path [RootComponent, UIComponent, SupportUIComponent].

DI- DependencyProvider , singleton- __DependencyProviderRegistry:

// Component.swift
public init(parent: Scope) {
     self.parent = parent
     dependency = createDependencyProvider()
}

// ...

private func createDependencyProvider() -> DependencyType {
    let provider = __DependencyProviderRegistry.instance.dependencyProvider(for: self)
    if let dependency = provider as? DependencyType {
        return dependency
    } else {
        // This case should never occur with properly generated Needle code.
        // Needle's official generator should guarantee the correctness.
        fatalError("Dependency provider factory for \(self) returned incorrect type. Should be of type \(String(describing: DependencyType.self)). Actual type is \(String(describing: dependency))")
    }
}

, DependencyProvider __DependencyProviderRegistry path. , . hash , :

// DependencyProviderRegistry.swift
func dependencyProvider(`for` component: Scope) -> AnyObject {
    providerFactoryLock.lock()
    defer {
        providerFactoryLock.unlock()
    }

    let pathString = component.path.joined(separator: "->")
    if let factory = providerFactories[pathString.hashValue] {
        return factory(component)
    } else {
        // This case should never occur with properly generated Needle code.
        // This is useful for Needle generator development only.
          fatalError("Missing dependency provider factory for \(component.path)")
    }
}

DependencyProvider dependency, .

:

protocol SomeUIDependency: Dependency {
    var applicationURLHandler: ApplicationURLHandler { get }
    var router: Router { get }
}

final class SomeUIComponent: Component<SomeDependency> {
    var someObject: SomeObjectClass {
        shared {
            SomeObjectClass(router: dependecy.router)
        }
    }
}

DependecyProvider.

DependencyProvider

, DI- DependencyProvider. . Needle DI- BootstrapComponent Component.

DI- .

. , .. .

.

, , . compile-time safety.

, , Needle DependecyProvider DI-. :

// NeedleGenerated.swift

/// ^->RootComponent->UIComponent->SupportUIComponent->SomeUIComponent
private class SomeUIDependencyfb16d126f544a2fb6a43Provider: SomeUIDependency {
    var applicationURLHandler: ApplicationURLHandler {
        return supportUIComponent.coreComponents.applicationURLHandler
    }
    // ...
}

- , , DependecyProvider . compile-time safety Needle.

.

DependencyProvider

DependecyProvider , Needle .

closure-, . .

registerProviderFactories(), - DI-.

// NeedleGenerated.swift
public func registerProviderFactories() {
    __DependencyProviderRegistry.instance.registerDependencyProviderFactory(for: "^->RootComponent") { component in
        return EmptyDependencyProvider(component: component)
    }
    __DependencyProviderRegistry.instance.registerDependencyProviderFactory(for: "^->RootComponent->UIComponent") { component in
        return EmptyDependencyProvider(component: component)
    }
        // ...
}   

singleton- __DependencyProviderRegistry. [Int: (Scope) -> AnyObject], hashValue , , — closure-. thread-safe NSRecursiveLock.

// DependencyProviderRegistry.swift
public func registerDependencyProviderFactory(`for` componentPath: String, _ dependencyProviderFactory: @escaping (Scope) -> AnyObject) {
    providerFactoryLock.lock()
    defer {
        providerFactoryLock.unlock()
    }

    providerFactories[componentPath.hashValue] = dependencyProviderFactory
}

430 . 83 Swift.

iPhone 11 c iOS 13.3.1 Needle 0.14.

— develop , root- needle-, Needle. .

Needle: 283.58s

Needle: 289.7s

, , Needle, +6 .

Needle: 35.8s

Needle: 35.48s

.

registerProviderFactories()

(): 0.000103

:

0.0001500844955444336
0.0000939369201660156
0.0000900030136108398
0.0000920295715332031
0.0001270771026611328
0.0000950098037719726
0.0000910758972167968
0.0000970363616943359
0.0000969171524047851
0.0000959634780883789

, Needle .

Needle (): 0.000085

C Needle (): 0.001143 (+0.001058)

C Needle + FakeComponents (): 0.002566

: SomeUIComponent :^->RootComponent->UIComponent->SupportUIComponent->SupportUIFake0Component->SupportUIFake1Component->SupportUIFake2Component->SupportUIFake3Component->SomeUIComponent

. , . , .

BabyloneUIComponent c Needle

Needle (): 0.000044

Needle (): 0.000058

Needle + FakeComponents ():0.000091

. , .

, Needle , DI-.

compile time safety .

. , Objective-C, .

. .

Needle , - . , .

, Needle , , , , .