How to validate empty or null return on retrofit?-CodePudding

I am making a login, but I would like to validate so that something can be done when the user does not exist or the password doesn't match. But I always get "[]" in the body and I do not know how to set that in an "if".

I tried if(response), if(response!=null) and more but nothing worked. It always catches it like "not null".

var post: List<UserData>?

val response: Call<List<UserData>> = service.userLogin(email, pass)
response.enqueue(object : Callback<List<UserData>> {

    override fun onResponse(call: Call<List<UserData>>, response: Response<List<UserData>>) {
        post = response?.body()
        println(post)

CodePudding user response：

If you are sure that you always get the response is "[]" in the body, it means that the response is not null, just an empty array even if the user is not existing or the pass is wrong.

Regards your code, I change a little bit:

override fun onResponse(call: Call<List<UserData>>, response: Response<List<UserData>>) {

                post = when (response.body().isNotEmpty()) {
                    true -> response.body()
                    false -> listOf<UserData>() // or null, because `post` is nullable
                }
                
                println(post)
            }

There are 3 methods to judge a list is empty/null

CodePudding user response：

    override fun onResponse(call: Call<List<UserData>>, response: Response<List<UserData>>) {
        if (response.body()?.isEmpty() == true) {
            println("Empty")
        } else {
            println("No empty")
        }
    }

With the help of the comment of down below I got the solution, thanks.