Singleton solution to manage SharedPreferences

MyPrefManager.kt

import android.content.Context
import androidx.preference.PreferenceManager

// concrete Singleton 
object MyPrefManager: SharedPreferencePrimitives() {

    // here specify preferences' names
    private const val attachment    = "attachment"

    //call it once
    fun init(context:Context, pref_name:String="", mode:Int = Context.MODE_PRIVATE){
        
        if(isInitialized()) return      // prevent multiple init
        pref    =   if(pref_name.isEmpty()) PreferenceManager.getDefaultSharedPreferences(context)
                    else                    context.getSharedPreferences(pref_name, mode)
        editor  = pref.edit()
    }

    fun setAttachment(useattach: Boolean) {
        attachment.put(useattach)
    }
    fun getAttachment() = attachment.getBoolean()
}

SharedPreferencePrimitives.kt

import android.content.SharedPreferences

abstract class SharedPreferencePrimitives(){

    // both are initialized in subclasses
    lateinit var editor:SharedPreferences.Editor
    lateinit var pref: SharedPreferences

    fun isInitialized() = ::pref.isInitialized && ::editor.isInitialized

    protected fun String.put(long: Long) {
        editor.putLong(this, long)
        editor.commit()
    }

    protected fun String.put(int: Int) {
        editor.putInt(this, int)
        editor.commit()
    }

    protected fun String.put(string: String) {
        editor.putString(this, string)
        editor.commit()
    }

    protected fun String.put(boolean: Boolean) {
        editor.putBoolean(this, boolean)
        editor.commit()
    }

    protected fun String.getLong()      = pref.getLong(this, 0)
    protected fun String.getInt()       = pref.getInt(this, 0)
    protected fun String.getString()    = pref.getString(this, "")!!
    protected fun String.getBoolean()   = pref.getBoolean(this, false)


    fun clearData() {
        if(!isInitialized()) return

        editor.clear()
        editor.commit()
    }

    fun removeKey(key:String){
        if(!isInitialized()) return
        editor.remove(key)
        editor.commit()
    }    
}