How to make a function that takes both Activity and Fragment as the context for an argument

Issue

I have the following function that can take an activity as an argument and when I call it from an Activity it works perfectly. Now that I want to call this function from a fragment but I can see there is an error in the editor saying 'Incompatible types: CargoFragment and Activity'. I tried replacing activity: Activity with context: Context.

The error I have is at 'is CargoFragment'

    fun getProductList(activity: Activity) {
        mFireStore.collection("abc")
            .get()
            .addOnSuccessListener { 
                .....
                .....
                .....

                    productList.add(product)
                }
                when (activity) {
                    is CargoActivity -> {
                        activity.success(productList)
                    }
                    is CheckoutActivity -> {
                        activity.success(productList)
                    }
                    is CargoFragment -> {
                        activity.success(productList)
                    }
                }
            }
            .addOnFailureListener { e ->
                Log.d("CheckTag", e.message!!)
                when (activity) {
                    is CargoActivity -> {
                        activity.hideProgressDialog()
                    }
                    is CheckoutActivity -> {
                        activity.hideProgressDialog()
                    }
                }
            }
    }

Solution

Don't pass activity to getProductList. As far as I understand, you are passing activity to execute some code when you get a response (success or failure). A better way to implement this is to expose callback lambdas.

Consider this approach:

fun getProductList(onSuccess: (List<Product>) -> Unit, onFailure:() -> Unit) {
    mFireStore.collection("abc")
            .get()
            .addOnSuccessListener {
                ...                  
                    productList.add(product)
                }
                onSuccess(productList)
            }
            .addOnFailureListener { e ->
                ...
                onFailure()
            }
}

Usage (in your activity and fragment):

getProductList(
    onSuccess = { list ->
        success(list) // whatever you want to do on success
    },
    onFailure = {
        hideProgressBar() // whatever you want to do on failure
    }
)

Answered By - Arpit Shukla