kotlin optional callback

In Kotlin, an optional callback is a mechanism used to pass a function as a parameter to another function, allowing the receiving function to call back or invoke the passed function at a later time. This is commonly used in asynchronous programming, where a function may take some time to complete its task, and the callback function is invoked once the task is finished.

Here are the steps to implement an optional callback in Kotlin:

1. Define the callback function type: Before using a callback, you need to define the function type that the callback will have. This is done using the typealias keyword followed by the desired function signature. For example, if you want a callback function that takes an integer parameter and returns nothing, you can define the type as follows:

typealias Callback = (Int) -> Unit

1. Create a function that takes a callback parameter: In your function, define a parameter that represents the callback function. You can give it any name you want, but make sure its type matches the callback function type defined in step 1. For example:

fun performTask(callback: Callback) {
    // Perform some task here
    // Once the task is finished, invoke the callback function
    callback(42)
}

1. Call the callback function: Inside the function where you want to use the callback, invoke it using the parameter name followed by parentheses and any required arguments. For example, if you want to invoke the callback with the integer value 42, you would write:

callback(42)

1. Pass a function as a callback: When calling the function that takes a callback, you can pass a function as the callback parameter. This can be an anonymous function, a lambda expression, or a named function reference. For example:

performTask { result ->
    println("Callback invoked with result: $result")
}

In this example, the lambda expression { result -> println("Callback invoked with result: $result") } is passed as the callback function.

That's it! You have implemented an optional callback in Kotlin. The callback function will be invoked at the appropriate time, and you can perform any desired actions inside it.