I have a function where I validate a product as you can see in this snippet:

private fun validateProduct() : Boolean{

        val newProductName = binding.etNewProductName.text.toString().trim()
        val newProductPrice = binding.etNewProductPrice.text.toString().trim()
        val newProductCategory = binding.spNewProductCategory.selectedItem.toString()



        return when{
            TextUtils.isEmpty(newProductName) -> {
                showErrorSnackBar(binding.root, "Product name cannot be empty.", true)
                false

            }
            TextUtils.isEmpty(newProductPrice) -> {
                showErrorSnackBar(binding.root, "Price cannot be empty.", true)
                false
            }

            //make sure the first element is not a valid category
            newProductCategory == binding.spNewProductCategory.getItemAtPosition(0) -> {
                showErrorSnackBar(binding.root, "Please select a valid category.", true)
                false
            }

            //check if the new product's name already exists in the Firestore collection.
            //if so, return false.

 


            else -> {
                true
            }

        }
    }

Edit: My logic in mind was to iterate over the documents. Check each document if document["name"].toString() == newProductName if so, return false and display an error snackbar.

CodePudding user response：

Is there a way to check a Firestore document if its certain field is equivalent to some value?

Sure, there is. As you already said, yes, you have to iterate over the collection, but not for getting all documents and checking the new product name on the client. You have to do that in a query. Assuming that you have a collection called "products", to check if a specific product name already exists, please use the following lines of code:

val db = FirebaseFirestore.getInstance()
val productsRef = db.collection("products")
Query queryByProductName = productsRef.whereEqualTo("productName", newProductName)
queryByProductName.get().addOnCompleteListener { task ->
    if (task.isSuccessful) {
        if (!task.result.isEmpty) {
            Log.d(TAG, "$newProductName already exists.")
        } else {
            Log.d(TAG, "$newProductName doesn't exist.")
        }
    } else {
        Log.d(TAG, "Error getting documents: ", task.exception)
    }
}