How to return value from the function in kotlin

Question

I am trying to return the boolean value from the function.

fun  validateDetails(jabberId:String, passwordText: String) {

            if(jabberId.isEmpty()){
                jabber_id.requestFocus()
                jabber_id.error="Jabber id can't be null."
                 return false
            }else if(jabberId.isBlank()){
             jabber_id.requestFocus()
             jabber_id.error="Jabber id can't be blank."
              return false
            }else if (passwordText.isNotEmpty()){
                password.requestFocus();
                password.error="Password can't be null."
                 return false
            }
             else{
                 return true
            }   

    }

Error: The boolean literal does not conform to the expected type Unit.

I know unit is the default return type in kotlin. How will i change this to boolean.

Remove the = before the curly brace. And please, indent your code properly. — JB Nizet
– JB Nizet, Commented Apr 8, 2017 at 14:55
@AnkurKhandelwal just added a litte explanation on what you need to do — Jefferson Tavares
– Jefferson Tavares, Commented Apr 8, 2017 at 15:03

Jefferson Tavares · Accepted Answer · 2017-04-09 15:26:24Z

16

Kotlin can only infer the returned type of a function when its a expression, so if your function has a body, you need to specify the returned type after the function paramameters

fun functionName(param: Type...): ReturnedType { 
    //function body
}

fun  validateDetails(jabberId:String, passwordText: String):Boolean {

            if(jabberId.isEmpty()){
                jabber_id.requestFocus()
                jabber_id.error="Jabber id can't be null."
                 return false
            }else if(jabberId.isBlank()){
             jabber_id.requestFocus()
             jabber_id.error="Jabber id can't be blank."
              return false
            }else if (passwordText.isNotEmpty()){
                password.requestFocus();
                password.error="Password can't be null."
                 return false
            }
             else{
                 return true
            }   

    }

As glee8e mentioned, this could be done using an expression. This is how it'd be done.

fun  validateDetails(jabberId:String, passwordText: String) = when {
    jabberId.isEmpty() -> {
        jabber_id.requestFocus()
        jabber_id.error="Jabber id can't be null."

        false
    }

    jabberId.isBlank() -> {
        jabber_id.requestFocus()
        jabber_id.error="Jabber id can't be blank."

        false
    }

    passwordText.isNotEmpty() -> {
        password.requestFocus();
        password.error="Password can't be null."
        false
    }

    else -> true  
}

edited Apr 9, 2017 at 15:26

answered Apr 8, 2017 at 14:59

Jefferson Tavares

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4 Comments

glee8e Over a year ago

Alternatively, you can convert this function body into a single expression, as it's just a big if expression.

Jefferson Tavares Over a year ago

Just updated my answer. Thank you for point that out. xD I'm still getting used with the power of Kotlin, so I didn't even think about that possibility

glee8e Over a year ago

Since you are using kotlin, I assume you are also using IDEA (created by the JetBrains, the team behind kotlin), the power of which is also something you should pay attention to. If you set the pointer inside the method body (of your anwser), it will suggest you to change it into an expression body.

Jefferson Tavares Over a year ago

Yeah, I've been playing with Intellij IDEA for 1 1/2 month only, so I'm still geting used to it. I didn't know this trick by the way. Thanks for the advice :)

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