kotlin - 为什么作者将localCacheBillingClient设计为lateinit？

Question

代码 A 来自项目play-billing-samples ，可以看到it .

不知道为什么作者设计了localCacheBillingClient如 lateinit ，导致代码有点复杂，if (::localCacheBillingClient.isInitialized == false) {...}被多次调用。

我想代码 B 可以很好用吧？

代码 A

class BillingRepository private constructor(private val application: Application) :
        PurchasesUpdatedListener, BillingClientStateListener {

     lateinit private var localCacheBillingClient: LocalBillingDb


    val subsSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        if (::localCacheBillingClient.isInitialized == false) {
            localCacheBillingClient = LocalBillingDb.getInstance(application)
        }
        localCacheBillingClient.skuDetailsDao().getSubscriptionSkuDetails()
    }

    val inappSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        if (::localCacheBillingClient.isInitialized == false) {
            localCacheBillingClient = LocalBillingDb.getInstance(application)
        }
        localCacheBillingClient.skuDetailsDao().getInappSkuDetails()
    }

   fun startDataSourceConnections() {
        Log.d(LOG_TAG, "startDataSourceConnections")
        instantiateAndConnectToPlayBillingService()
        localCacheBillingClient = LocalBillingDb.getInstance(application)
    }
    ...
}

代码 B

class BillingRepository private constructor(private val application: Application) :
        PurchasesUpdatedListener, BillingClientStateListener {

    private val localCacheBillingClient: LocalBillingDb by lazy {
         LocalBillingDb.getInstance(application)
    }

    val subsSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        localCacheBillingClient.skuDetailsDao().getSubscriptionSkuDetails()
    }


    val inappSkuDetailsListLiveData: LiveData<List<AugmentedSkuDetails>> by lazy {
        localCacheBillingClient.skuDetailsDao().getInappSkuDetails()
    }

   fun startDataSourceConnections() {
        Log.d(LOG_TAG, "startDataSourceConnections")
        instantiateAndConnectToPlayBillingService()        
    }
    ...
}

Answer 1

Kotlin - Property initialization using "by lazy" vs. "lateinit"

我相信答案就在这个线程中，并且正好低于这一点。

lateinit var 可以从任何可以看到对象的地方初始化，例如从框架代码内部，单个类的不同对象可能有多个初始化场景。 by lazy { ... } 依次定义了该属性的唯一初始值设定项，它只能通过覆盖子类中的属性来更改。如果您希望您的属性以一种可能事先未知的方式从外部初始化，请使用 lateinit。