LAZY LOADING
There are several benefits to lazy loading. Lazy loading can result in faster startup time, since loading is deferred to when the variable is accessed. This is particularly useful in using Kotlin for an Android app as opposed to a server app. For Android apps, we want to reduce app startup time so that the user sees the app content faster, rather than sitting at an initial loading screen.
Lazy loading like this is also more memory efficient, as we only load the resource into memory if it is called upon. Memory usage is important on mobile platforms like Android since phones have limited, shared resources. For example, if you are creating a shopping app, and there is a possibility that users will only browse your selection, you could have the actual purchasing API be lazy-loaded:
val productsApi: ProductsApi by lazy {
val retrofit: Retrofit = Retrofit.Builder()
.baseUrl(API_URL)
.addConverterFactory(MoshiConverterFactory.create())
.build()
retrofit.create(ProductsApi::class.java)
}
By using lazy loading like this, if the user never attempts to check out in the app, you will never load the PurchasingApi, and therefore will not use up the resources it would take.
Lazy loading is also a good way to encapsulate initialization logic:
// bounds is created as soon as the first call to bounds is made
val bounds: RectF by lazy {
RectF(0f, 0f, width.toFloat(), height.toFloat())
}
As soon as the first reference to bounds is made, the RectF is created, using the view’s current width and height, saving us from having to explicitly create this RectF, then set it later on.
Proud Geek 