Kotlin
Putting it together
Combine all parts into a working final app.
Putting it together: the full flow
In the final lesson you combine all pieces: adding tasks, completing one and printing the completed ones. The app becomes a small sample of a real task tracker.
val list = TaskList()
list.addTask("Study Kotlin")
list.addTask("Shopping")
list.complete(0)
println(list.listDone())
// [[x] Study Kotlin]
This flow calls addTask, complete and listDone one after another. Each is a piece you defined in previous lessons. This completes a real use case.
Flow design
The app flow is: first add tasks to the list, then complete one, finally print the completed ones. Each step calls a method defined in earlier lessons.
list.addTask("Study Kotlin") // L02
list.addTask("Shopping") // L02
list.complete(0) // L04
println(list.listDone()) // L03
This flow shows the power of cumulative design. Each lesson added one piece and the final lesson put them together. In the real world, apps grow this way too.
Exercise Combine the whole flow
In main create val list = TaskList(). Call list.addTask("Study Kotlin") and list.addTask("Shopping"). Complete the first task with list.complete(0). Finally print list.listDone() with println.
Show example solution
class Task(val title: String) {
var done: Boolean = false
override fun toString(): String {
return if (done) "[x] $title" else "[ ] $title"
}
}
class TaskNotFound(message: String) : Exception(message)
class TaskList {
val tasks = mutableListOf<Task>()
fun addTask(title: String) {
tasks.add(Task(title))
}
fun listDone() = tasks.filter { it.done }
fun complete(index: Int) {
if (index >= tasks.size) throw TaskNotFound("Görev yok: $index")
tasks[index].done = true
}
}
fun main() {
val list = TaskList()
list.addTask("Study Kotlin")
list.addTask("Shopping")
list.complete(0)
println(list.listDone())
}
Test yourself
-
Match method to purpose
- addTask
- Add task
- complete
- Finish task
- listDone
- Get done tasks
- TaskNotFound
- Error type
-
How are branches chosen in this project?
- Only for
- Only if
- with when branches
- Only try
Show answer
with when branches — The project flow uses when branches.
-
Fill in the blank: call complete
try {
list.____(0)
} catch (e: TaskNotFound) {
println(e.message)
}
Show answer
try {
list.complete(0)
} catch (e: TaskNotFound) {
println(e.message)
}
Next lesson: Beginner section exam
