Run an action right after lazy object initialisation

Question

Do we have a way to do some action with a lazy initializing object right after creation?

For example, smth like this:

val lazyInitObject by createLazyObject()
   .apply {
       // do some action with just created lazyInitObject
   }

Could you please elaborate on your use case? Also, what is createLazyObject() here? Last but not least, is this initialization intended to change the state of the object itself or the containing class? — Joffrey
– Joffrey, Commented Feb 1, 2022 at 12:09

Joffrey · Accepted Answer · 2022-02-01 12:11:35Z

7

Not sure what your createLazyObject() is here, but with the standard lazy delegate you have full control over the initialization lambda:

val lazyInitObject by lazy {
   createTheValue().also {
       // do something with it
   }
}

So if you want to allow this kind of thing you might want to design your custom delegate differently so it accepts a lambda.

Note that if what you want to do is only about changing the state of the lazily created object and not the enclosing class, you may want to simply use an init { } block in the object's class itself.

answered Feb 1, 2022 at 12:11

Joffrey

38.3k8 gold badges90 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Andrew Kolubov Over a year ago

Here in also our context is Lazy<T> instead of T. So, I can't get access to created object.

Andrew Kolubov Over a year ago

ok, find my error. It's on incorrect question. Sorry. Your answer here is correct.

Benjamin Charais · Accepted Answer · 2022-02-01 19:59:41Z

Using the build in object I can describe some of how Kotlin will allow you to do this, and will allow you to define this more specifically for your use case. This can absolutely be accomplished with built in tools, if you need a more specific usage, the .also {} standard function will help you tack on functionality after any call

object MyObject {
 
    fun myFunctions() {
        println("I have done my work - MyObject")
    }
    
    init {
        // Calls on first reference...
        println("Hello world! - I am initialized - MyObject")
    }
}

println("My app has started")
MyObject.myFunctions()

/*
   This prints:
     My app has started
     Hello world! - I am initialized - MyObject
     I have done my work - MyObject
*/

interface ILazy {
    fun myFunction()
}

val myLazy: ILazy by lazy {
    val myObject = object : ILazy { 
        override fun myFunction() {
            println("myLazy has done its work")
        }
        
        init {
            println("Object declarative is run instantly - MyLazy")
        }
    }
    
    println("Post object declaration - Lazy")
    myObject
}

myLazy.myFunction()
/*
  This prints:
    Object declarative is run instantly - MyLazy
    Post object declaration - Lazy
    myLazy has done its work
*/

Collectives™ on Stack Overflow

Run an action right after lazy object initialisation

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related