android kotlin - takeIf and takeUnless example

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.os.Bundle
import android.text.method.ScrollingMovementMethod
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // get the widgets reference from XML layout
        val textView = findViewById<TextView>(R.id.textView)
        val btnList = findViewById<Button>(R.id.btnList)
        val btnTakeIf = findViewById<Button>(R.id.btnTakeIf)
        val btnTakeUnless = findViewById<Button>(
            R.id.btnTakeUnless)


        // make textview content scrollable
        textView.movementMethod = ScrollingMovementMethod()


        val list = generateList()

        btnList.setOnClickListener {
            textView.text = "Employees:\n"
            // Iterate through the list
            list.forEach {
                textView.append("\n${it.name} : age ${it.age}" +
                        " : salary $${it.salary}")
            }
        }


        btnTakeIf.setOnClickListener {
            textView.text = "Take if list is not empty:\n"
            list.takeIf {
                it.isNotEmpty() // required boolean
            }.apply {
                this?.forEach {
                    // do the task
                    textView.append("\n" + it.name)
                }
            }
        }


        btnTakeUnless.setOnClickListener {
            textView.text = "Take unless list is empty:\n"
            list.takeUnless {
                it.isEmpty()// required boolean
            }.apply {
                this?.forEach {
                    // do the task
                    textView.append("\n" + it.name)
                }
            }
        }
    }
}



// Method to generate employee list
private fun generateList():MutableList<Employee>{
    val list = mutableListOf<Employee>()
    list.add(Employee("Weston",25,6500))
    list.add(Employee("Gregg",29,5400))
    list.add(Employee("Erika",24,5200))
    list.add(Employee("Ashly",19,4900))
    list.add(Employee("Tristian",20,2600))
    list.add(Employee("Violette",23,4650))
    list.add(Employee("Viviane",37,5100))
    list.add(Employee("Kyra",48,4100))
    list.add(Employee("Uriel",19,2300))
    list.add(Employee("Isaias",16,6800))
    return list
}


// Data class for Employee
data class Employee(
    val name:String,
    val age:Int,
    val salary:Int
)

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#F8F8F8"
    android:padding="24dp">

    <Button
        android:id="@+id/btnList"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="List"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnTakeIf"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:text="takeIf"
        android:textAllCaps="false"
        app:layout_constraintBottom_toBottomOf="@+id/btnList"
        app:layout_constraintStart_toEndOf="@+id/btnList" />

    <Button
        android:id="@+id/btnTakeUnless"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:text="takeUnless"
        android:textAllCaps="false"
        app:layout_constraintBottom_toBottomOf="@+id/btnTakeIf"
        app:layout_constraintStart_toEndOf="@+id/btnTakeIf" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginTop="16dp"
        android:fontFamily="sans-serif"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btnList" />

</androidx.constraintlayout.widget.ConstraintLayout>

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