Expect member declaration error on declared variables in kotlin-CodePudding

I'm a beginner in kotlin and I'm getting errors on my variables when I tried using them. please I need help. Here is my code

package com.example.myapplication
import java.util.*
class savedData(hour:Int, Minutes:Int) {
  var calendar= Calendar.getInstance()
  calendar.set(Calendar.HOUR_OF_DAY,hour )
  calendar.set(Calendar.MINUTE,Minutes )
  calendar.set(Calendar.SECOND,0 )
}

I get errors when i use the calendar variable in my code above

CodePudding user response：

Your various calendar.set calls need to be inside an init block:

class savedData(hour: Int, minutes: Int) {

    var calendar = Calendar.getInstance()

    init {
        calendar.set(Calendar.HOUR_OF_DAY, hour)
        calendar.set(Calendar.MINUTE, minutes)
        calendar.set(Calendar.SECOND, 0)
    }
}

Class-level statements can only be property declarations, not code to initialize them.

Another approach would be to use a scoping function like apply:

class savedData(hour: Int, minutes: Int) {

    var calendar = Calendar.getInstance().apply {
        set(Calendar.HOUR_OF_DAY, hour)
        set(Calendar.MINUTE, minutes)
        set(Calendar.SECOND, 0)
    }
}

CodePudding user response：

This will work:

class savedData(hour:Int, Minutes:Int) {
     var calendar= Calendar.getInstance().apply{
         this.set(Calendar.HOUR_OF_DAY,hour )
         this.set(Calendar.MINUTE,Minutes )
         this.set(Calendar.SECOND,0)
     }
}

Within a class body, its properties and methods are declared. The executable code must be inside these methods (or in init {} block, or in some setters/getters, or in scope functions like above), not in the body of the class.

CodePudding user response：

The other 2 answers are basically correct. However, you might also be interested in initializing the property the lazy way, so that it won't be initialized as long as nothing needs it:

class savedData(hour:Int, Minutes:Int) {
    var calendar: Calendar by lazy {
        Calendar.getInstance().apply {
            set(Calendar.HOUR_OF_DAY, hour)
            set(Calendar.MINUTE, Minutes)
            set(Calendar.SECOND, 0)
        }
    }
}

This is specially useful for creating an instance of a class with resource-intensive init process.