Passing function as parameter in kotlin

Question

I'm trying to pass a function as a parameter but it throws 'Unit cannot be invoked as function. Thanks in advance.

uploadImageToParse(imageFile, saveCall1())
uploadImageToParse(imageFile, saveCall2())
uploadImageToParse(imageFile, saveCall3())

private fun uploadImageToParse(file: ParseFile?, saveCall: Unit) {
        saveCall()//Throws an error saying 'Unit cannot be invoked as function'
} 

Answer 1

Problem is, that you are not passing a function as a parameter to the uploadImageToParse method. You are passing the result. Also uploadImageToParse method is expecting safeCall to be Unit parameter not a function.

For this to work you have to first declare uploadImageToParse to expect a function parameter.

fun uploadImageToParse(file: String?, saveCall: () -> Unit) {
    saveCall()
}

Then you can pass function parameters to this method.

uploadImageToParse(imageFile, {saveCall()})

For more information on the topic take a look at Higher-Order Functions and Lambdas in the Kotlin documentation.

Edit: As @marstran pointed out, you can also pass the function as a parameter using Function Reference.

uploadImageToParse(imageFile, ::saveCall)