How to add user in Map using dataclass, Kotlin - android-studio

Question

So I want to add user in map and then check if it's added in there.
for instance, user enters their information, im saving their email as key and information in dataclass as value
private val users = mutableMapOf<String, User>()
private fun add(){
check()
val email = binding.email.text.toString()
val firstName = binding.firstname.text.toString()
val lastName = binding.lastname.text.toString()
val age = binding.age.text.toString()
users["default"] = User("email","firstName","lastName","age")
for (user in users.keys){
if (email == user) {
Toast.makeText(this,"not successful",Toast.LENGTH_SHORT).show()
break
}else{
users[email] = User(email,firstName,lastName,age)
Toast.makeText(this,"successful",Toast.LENGTH_SHORT).show()
}
}
}
but when i click on the button in first run, it just says successful, but on the second click it should return not successful because this user was already created, but it shows both toasts.
can u tell me why it does this and how can i fix it?

Answer 1

this has to do with the fact that the for loop has no guarantee that it will iterate the keys in the order you expect.
For example, consider this map:
users["default"] = User("email","firstName","lastName","age")
users["zzz#xyz.com"] = User("email","zz","z","age")
suppose that the keys would be iterated in alphabetical order(this is not actually the case most of the time) and that you had email=zzz#xyz.com
On the first iteration, the user string would refer to default. Since email == user is false, it would go to the else branch of your loop. Then, on the next iteration, user will be zzz#xyz.com and email == user will be true; just sending the "toast" notification twice.
It seems that you're trying to insert an element if it doesn't exists, or show an error if it does. Instead of a for loop, consider checking for the existence of the previous key with containsKey and then adding a new element if necessary.
// In kotlin, you can create a map with initial values by using the "to" infix function
private val users = mutableMapOf<String, User>(
"default" to User("email","firstName","lastName","age")
)
private fun add() {
check()
val email = binding.email.text.toString()
val firstName = binding.firstname.text.toString()
val lastName = binding.lastname.text.toString()
val age = binding.age.text.toString()
if (users.containsKey(email)) {
Toast.makeText(this,"not successful",Toast.LENGTH_SHORT).show()
return
}
users[email] = User(email,firstName,lastName,age)
Toast.makeText(this,"successful",Toast.LENGTH_SHORT).show()
}

Answer 2

This is because you are comparing the map key with the email value. You need to compare the value of the email. Try to do as follows within the for: email == user.value.email.