CODEWITHSUNDEEP
androidasynchronouskotlinlambda
mgcation
mgcation

Reputation: 547

Asynchronous anonymous function in Kotlin? (lambda expressions)

I'm making a listview (android) what call function when click.

and I want to get function is async or sync.

to block when it is async.

and even i want to know how attach async mark to kotlin lambda expression.

class FunctionCaller_Content(text: List<String>,
                             val function: List<    /*suspend? @async? */
                                                    (    () -> Unit    )?
                                               >? = null)
                                                 /* I want both of async, sync function. */
{

    fun isAsnyc(order: Int): Boolean
        = // how to get this lambda expression{function?.get(order)} is async?

    fun call(callerActivity: Activity, order: Int) {
        val fun = function?.get(order)
        fun()
        if(isAsync(fun))
            /* block click for async func */
    }

}

and usage.

FunctionCaller_Content( listOf("Click to Toast1", "Click to Nothing"),
                        listOf(
                        {
                            Toast.makeText(this, "clicked", Toast.LENGTH_SHORT)
                        },
                        {
                            /*if async lambda expression, how can i do?*/
                        } )

Upvotes: 4

Views: 3033

Answers (1)

Alexey Romanov
Alexey Romanov

Reputation: 170919

You can have List<suspend () -> Unit>, but you can't have both suspend and non-suspend functions in the same list except by using List<Any>. I'd suggest using two separate lists instead. Another solution is to use "algebraic data type":

sealed class SyncOrAsync // can add methods here
class Sync(val f: () -> Unit) : SyncOrAsync
class Async(val f: suspend () -> Unit) : SyncOrAsync

class FunctionCaller_Content(text: List<String>,
                             val function: List<SyncOrAsync>? = null)
{

    fun call(callerActivity: Activity, order: Int) {
        val fun = function?.get(order)
        if(fun is Async)
            /* block click for async func */
    }

}

FunctionCaller_Content( 
    listOf("Click to Toast1", "Click to Nothing"),
    listOf(Sync {
               Toast.makeText(this, "clicked", Toast.LENGTH_SHORT)
           },
           Async {
               // your async code
           })

But if you are just going to block anyway, I would just use List<() -> Unit> and

listOf({
           Toast.makeText(this, "clicked", Toast.LENGTH_SHORT)
       },
       {
           runBlocking {
               // your async code
           }
       })

Upvotes: 5

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