通过将类作为函数参数传递来调用类方法的 Swift 依赖注入(inject)

Question

我可能以错误的方式处理这个问题，但我想为单元测试目的引入依赖注入(inject)，为此我需要将一个类作为参数传递。在某种伪代码中，它应该如下所示:

protocol LocalSavingProtocol {
    static func saveDataLocally()
}

class ProductionClass: LocalSavingProtocol {
    static func saveDataLocally() {
        print("actually save data")
    }
}

class TestClass: LocalSavingProtocol {
    static func saveDataLocally() {
        print("test saving data")
    }
}

func saveEverywhere(injecting localSavingClass: LocalSavingProtocol = ProductionClass) {
    localSavingClass.saveDataLocally()
}

//production code
saveEverywhere()

//test
saveEverywhere(injecting: TestClass)

显然这是行不通的，尽管我尝试通过传递 .Type 或 .self，更改 saveEverywhere 函数到

saveEverywhere<T: LocalSavingProtocol>(injecting localSavingClass: T)

等等，没有任何效果。

目标是拥有这样一个系统:

1. 我可以在测试代码时注入(inject)一个类
2. 我不必在生产代码中注入(inject)类(即有一个默认值)
3. 我可以在注入(inject)类上调用类方法

Answer 1

protocol LocalSavingProtocol {
    static func saveDataLocally()
}

class ProductionClass: LocalSavingProtocol {
    class func saveDataLocally() {
        print("actually save data")
    }
}

class TestClass: LocalSavingProtocol {
    class func saveDataLocally() {
        print("test saving data")
    }
}

func saveEverywhere(injecting localSavingClass: LocalSavingProtocol.Type = ProductionClass.self) {
    localSavingClass.saveDataLocally()
}

//production code
saveEverywhere()

//test
saveEverywhere(injecting: TestClass.self)