如何从kotlin中的函数返回值

Question

我正在尝试从函数返回布尔值。

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
            }   

    }

错误：布尔文字不符合预期的类型单位。

我知道unit是kotlin中的默认返回类型。我将如何将其更改为布尔值。

Answer 1

当函数是表达式时，Kotlin只能推断其返回的类型，因此如果函数有一个主体，则需要在函数参数后面指定返回的类型

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
            }   

    }

正如glee8e所提到的，这可以使用表达式来完成。这是怎么做到的。

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  
}