Lets say I have the following lines
repository.findUser(name = "John Doe")
.map {
// User was found, continue processing
}
.switchIfEmpty(
// Just log that the user was not found
)
My non-best-practice-but-working approach currently is to just put the logging in another function and call it, like switchIfEmpty(userNotFound())
private fun userNotFound(): Mono<out Disposable> {
logger.info { "No user was found." }
return Mono.empty()
}
This works but I cannot imagine this is what I should be doing. How can I improve?
One way is to use the Mono.defer inside switchIfEmpty:
repository.findUser(name = "John Doe")
.switchIfEmpty(Mono.defer{ ... })
Alternatively, you could use doOnSuccess and check if Mono has completed without data(sample in Java):
repository.findUser(name = "John Doe")
.doOnSuccess(e -> {
if (e == null) {
log.info("No user was found.");
}
})
Related
there're several elements inside configTypeBuilderList, if the value in ruleAttributes not same as the destinationField in ConfigTypeBuilder, it will log the error
ruleCriteriaList.forEach { configRuleCriteria ->
validateConfigTypeBuilder(configRuleCriteria.configTypeBuilderList, ruleAttributesNames)
}
private fun validateConfigTypeBuilder(configTypeBuilderList: List<ConfigTypeBuilder>, ruleAttributes: List<String>) {
val missAttributeList: MutableList<String> = mutableListOf()
configTypeBuilderList.forEach { configTypeBuilder ->
if(configTypeBuilder!= null) {
if (ruleAttributes.firstOrNull { ruleAttribute -> ruleAttribute == configTypeBuilder.destinationField } == null) {
if(!ruleAttributes.contains(configTypeBuilder.destinationField)) {
missAttributeList.add(configTypeBuilder.destinationField)
}
logger.error("{} is wrong", configTypeBuilder.destinationField)
}
}
}
The problem is each time there's only one element(configTypeBuilderList) go into validateConfigTypeBuilder, so the logger shows like this
logger.error("field1 is wrong")
logger.error("field2 is wrong")
...
What I need is, how can I modify my code in order to do this?
logger.error("field1, field2, field3 are wrong")
Edit
I tried the first solution, but I stuck here, I still get the same error result, the reason is because each time there's only one "destinationField", how can I make the list have all the error field, and then log the error, can I use continue or something?
Here are a couple of alternatives:
Add them to a list and log later.
fun foo()
val incorrectItems = mutableListOf<Any>()
// Do some stuff
// on error:
incorrectItems.add(someIncorrectItem)
// Do more stuff
// log the accumulated errors:
logger.error("${incorrectItems.joinToString("")} are wrong")
}
Partition your list into valid and invalid values. Log the invalid ones and process the good ones.
fun foo(someList: List<MyClass>) {
val (goodItems, badItems) = someList.partition { it.isValid() }
// ...where isValid() is whatever code you need to check is OK.
if (badItems.isNotEmpty()) {
logger.error("${badItems.joinToString("")} are wrong")
}
// Do stuff with goodItems
}
This is my first time using Kotlin, I have to write a simple command-line application where it takes a list of user input strings. Valid inputs are only "Apple" or "Orange" and calculate the price (which is 60 cents and 25 cents respectively). I'm having some trouble with the 3rd requirement
"Build a service that listens for when orders are complete and sends a notification to the customer regarding its status and estimated delivery time. The Mail service subscribes to events from the Orders service and publishes the appropriate event that the customer (you) is able to read from the terminal"
this is what I have done so far
MainApp.tk
import java.util.Scanner
import kotlin.system.exitProcess;
import app.Checkout;
var shopRunning = true;
var applecount = 0;
fun main(args: Array<String>) {
while (shopRunning) {
println("Welcome to Express Store");
println("1. Checkout");
println("2. exit");
var userOption = 0;
//request the user to eneter an option
//if user eneter a options that is not valid it will keep looping til option that is enterd is accepted;
var userSeletedOption = false;
val inputScanner = Scanner(System.`in`);
while (!userSeletedOption) {
print("Select an Option: ");
userOption = inputScanner.nextInt();
//if input entered by the user is not accepted and invaliud message is printed and is promted to enter an option again.
if (userOption != 1 && userOption != 2) {
println("Invalid input detected!");
} else {
userSeletedOption = true;
}
}
if (userOption == 1) {
val checkout = Checkout();
println("We currently have apples and oranges in Stock.")
var list: MutableList<String> = ArrayList();
println(list.size);
var doneAddingToCart = false;
while(!doneAddingToCart){
print("enter name of item to be enter or exit to finish adding to the cart: ")
var item = inputScanner.next();
if(item.equals("exit")){
doneAddingToCart=true;
}
else{
list.add(item);
}
}
if(checkout.verify(list)){ //checks if list has any item that is not an apple or orange
println("Thank you for your Pruchse");
val cost = checkout.Chasher(list)
println("You bought: "+ list.toString());
print("your total is: "+ cost);//returns the total cost
exitProcess(1);//exits from the application
}
} else if (userOption == 2) {
print("Have a great day.");
exitProcess(1);
}
}
}
CheckOut.tk
class Checkout {
//checks if the user entered any invaild items
public fun verify (cart: MutableList<String>) : Boolean{
for(item in cart){
if(!item.equals("Apple") && !item.equals("Orange")){
return false;
}
}
return true;
}
public fun Chasher (cart: MutableList<String>) : Double{
var total = 0.0;
var orangecount = 0;//step 2 offers
var applecount = 0;//step 2 offers
for(item in cart){//step 1 function
if(item.equals("Apple") || item.equals("apple")){
applecount+=1;
total= total + 0.6;
}
if(item.equals("Orange") || item.equals("orange")){
orangecount +=1;
total=total +0.25;
}
}
if(orangecount ==3){//buy three for the price of 2.step 2
println("You qaulidified for our buy 3 oragnes for the price of 2 offer")
total -=0.25;
}
if(applecount ==1){//buy one aple get 1 free. step 2
println("You buy 1 apple get one free")
cart.add("Apple");
}
return total;
}
}
I don't need to send an email just send a message to the command line. Currently, I'm just printing messages (just to see if what I currently have even works). Yeah, I know there many spelling errors, english and writing was never my strongest subject
I can only provide three hints that might help you:
If you exit your program using System.exit, use 0 if the run did not have any problem. (Excerpt from JavaDoc: "The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.")
For checking equality, simply use == which corresponds to equals in Java. In your special case however, you can use item.equals("apple", ignoreCase=true) or simply item.equals("apple", true).
I'm not sure what the author of your task exactly expects as a solution.
In can imagine you are expected to use lambdas.
An example: Your could refactor your Checkout class like that:
class Checkout {
/**
* Checks if the given [cart] contains only apples and oranges,
* and calls [onSuccess].
* If also other articles are contained, [onSuccess] is not called.
*/
fun verify(cart: List<String>, onSuccess: (List<String>) -> Unit): Unit {
for (item in cart) {
if (!item.equals("apple", true) && !item.equals("Orange", true)) {
return
}
}
onSuccess(cart)
}
}
And then call
val cart = listOf("Orange", "Apple", "apple", "orange")
Checkout().verify(cart, { cart: List<String> ->
println("Thanks you for your purchase: $cart")
})
or even shorter (curly brackets are outside of parenthesis)
Checkout().verify(cart) { cart: List<String> ->
println("Thanks you for your purchase: $cart")
}
What I did here was to extract what is executed if your validation succeeds:
For that, I used a lambda function that accepts a list of articles/strings (List<String>) and returns something I ignore/don't care about -> Unit.
The advantage of that approach is that callers of your verify method can decide what to do on success at their liking because they can pass a lambda function around like any other variable. Here:
val cart = listOf("Orange", "Apple", "apple", "orange")
val onSuccess = { cart: List<String> ->
println("Thanks you for your purchase: $cart")
}
Checkout().verify(cart, onSuccess)
You could also extend Checkout to allow an observer to register.
I deliberately kept the code very simple. Normally you would allow multiple observers to register, only expose what clients are supposed to see and hide the rest, etc.
class Checkout(
val onSuccess : (List<String>) -> Unit
) {
fun verify(cart: List<String>): Unit {
for (item in cart) {
if (!item.equals("apple", true) && !item.equals("Orange", true)) {
return
}
}
onSuccess(cart)
}
}
val checkout = Checkout({ cart: List<String> ->
println("Thanks you for your purchase: $cart")
})
and then
val cart = listOf("Orange", "Apple", "apple", "orange")
checkout.verify(cart)
Be sure to check out https://play.kotlinlang.org/byExample/04_functional/01_Higher-Order%20Functions to learn more about lambda / higher-order functions.
I was trying to implement live typeface change's in the edittextview
based on markdown syntax
and the first code I do was
my_edit_text_view.text = makeMDStyleSpannable(my_edit_text_view.text)//returns spannableString
but no luck since it is not invoking every time when text is changed
so I gave another try which is creating listener and testing things are working properly before I jump
my_edit_text_view.text = doOnTextChanged { it, start, count,after ->
if (it != null) {
if(it.isNotEmpty()){
Toast.makeText(this, (makeMDStyleSpannable(it)), Toast.LENGTH_SHORT).show()
}else if(it.isNullOrEmpty()){
}
}
}
as result it worked on another TOAST
However, here's the real recurring happened
my_edit_text_view.text = doOnTextChanged { it, start, count,after ->
if (it != null) {
if(it.isNotEmpty()){
my_edit_text_view.text = (makeMDStyleSpannable(it)
}else if(it.isNullOrEmpty()){
}
}
}
umm, what actually happening is while there is external text change(keyboard) on the edittext it calls makeMDStyleSpannable and this apply internal change then again and again it will call doOnTextChanged, Finally crashes.
How could I solve this problem?
keyboard(onText added[external]) => startThelistner => makeMDStyleSpannable[in]
/\ ||
||=====[infinite]=======
thanks
You can solve it by adding a boolean to check if text is changed by user or the code.
val shouldIgnoreChange = false
my_edit_text_view.text = doOnTextChanged { it, start, count,after ->
if (it != null) {
if(it.isNotEmpty()){
if(!shouldIgnoreChange){
shouldIgnoreChange = true
my_edit_text_view.text = (makeMDStyleSpannable(it)
shouldIgnoreChange = false
}
}else if(it.isNullOrEmpty()){
}
}
}
I'm nearly done creating an app that sends txt files, containing scanned data, to an ftp server.
The issue that I'm currently struggling with is: what if my Wi-Fi has terrible signal or no signal at all.
I noticed that my 'isOnline()' check works fine and that if there is no internet, it alerts the user. However a few hours ago I tested the app in the basement and noticed that when the Wi-Fi signal has no bars, it still sends the data but it gets lost somewhere along the way.
Currently the flow of the data is as follow:
user presses 'send'
check internet and if true, continue
clear content list and send
the content to viewmodel
viewmodel checks internet again before
creating the txt files
txt files get sent via FTP code below.
private fun sendTXT(result: String) {
try {
val name = "00_VER${LocalDateTime.now().format(fileNameFormatter)}.txt"
val path = getApplication<Application>().applicationContext.filesDir.path
.toString() + name
val f = File(path)
val isNewFileCreated: Boolean = f.createNewFile()
if (isNewFileCreated) {
f.writeText(result, Charsets.UTF_8)
}
val ftpClient = FTPClient()
ftpClient.addProtocolCommandListener(PrintCommandListener(PrintWriter(System.out)))
ftpClient.connect("xxx.xx.xxx.xx", 21)
val reply: Int = ftpClient.replyCode
if (!FTPReply.isPositiveCompletion(reply)) {
ftpClient.disconnect()
throw IOException("Exception in connecting to FTP Server")
}
if (ftpClient.login("username", "pass")) {
ftpClient.enterLocalPassiveMode()
ftpClient.setFileType(FTP.BINARY_FILE_TYPE)
val inp = FileInputStream(f)
var directory = "/files/input"
ftpClient.changeWorkingDirectory(directory)
val result = ftpClient.storeFile(name, inp)
inp.close()
if (result) {
ftpClient.logout()
ftpClient.disconnect()
f.delete()
}
}
} catch (e: Exception) {
e.printStackTrace()
}
}
fun isOnline(context: Context): Boolean {
var result = false
val connectivityManager =
context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
val networkCapabilities = connectivityManager.activeNetwork ?: return false
val actNw =
connectivityManager.getNetworkCapabilities(networkCapabilities) ?: return false
result = when {
actNw.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> true
actNw.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> true
actNw.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> true
else -> false
}
} else {
connectivityManager.run {
connectivityManager.activeNetworkInfo?.run {
result = when (type) {
ConnectivityManager.TYPE_WIFI -> true
ConnectivityManager.TYPE_MOBILE -> true
ConnectivityManager.TYPE_ETHERNET -> true
else -> false
}
}
}
}
return result
}
I'm stuck at finding a way to make sure the data gets to the server. Is there a more advanced way to check for internet connectivity?
I was considering adding all the scan objects as JSON to sharedpreferences, and if at the end of the day the user notices a scan didn't make it through, they can look up the missing scan and resend it.
However this seems very unconventional and I'm pretty sure there must be a better way to handle things.
New to Reactive Java here. Can someone please help with this simple scenario (written in Kotlin):
fun testReactive(): Int {
Mono.just("item-exists-in-database")
.onErrorReturn("item-missing") // if item is not in database an exception will be thrown
.map { item ->
if (item == "item-exists-in-database") {
Mono.just("deleting")
.doOnSuccess { println("deleting item") } // <-- this never prints!
} else {
Mono.just("ok")
}
}.map {
println("Creating item in database")
Mono.just("creating item in database")
}.block()
return 0
}
Running it produces:
Creating item in database
Why doesn't the line "deleting item" ever print?
you could consider the switchIfEmpty operator
https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html#switchIfEmpty-reactor.core.publisher.Mono-