Why Flow matters for async sequences in Kotlin - See It in Action

Why Flow matters for async sequences

📖 Scenario: Imagine you want to get updates about the weather every second. You want to see the temperature change live without waiting for all data at once.

🎯 Goal: You will create a simple Kotlin program using Flow to emit temperature updates every second and print them as they arrive.

📋 What You'll Learn

Create a Flow that emits temperature values

Use a configuration variable for the number of updates

Collect the Flow asynchronously and print each temperature

Understand why Flow helps with asynchronous sequences

💡 Why This Matters

🌍 Real World

Flow is used in apps to handle live data streams like sensor readings, user inputs, or network updates smoothly.

💼 Career

Understanding Flow is important for Kotlin developers working on Android apps or backend services that need to process asynchronous data efficiently.

1

Create a Flow emitting temperatures

Create a Flow called temperatureFlow that emits these exact temperature values: 20, 21, 22, 23, 24.

Kotlin

# Your code here

Need a hint?

Use flow { emit(value) } to create a Flow that sends values one by one.

2

Add a configuration variable for update count

Create an Int variable called updateCount and set it to 5 to represent how many temperature updates to expect.

Kotlin

import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.flow

val temperatureFlow: Flow = flow {
    emit(20)
    emit(21)
    emit(22)
    emit(23)
    emit(24)
}

# Your code here

Need a hint?

Just create a simple integer variable with the exact name and value.

3

Collect the Flow asynchronously and print values

Write a suspend function called printTemperatures that collects temperatureFlow and prints each temperature with println. Use a for loop with temperature as the variable.

Kotlin

import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.flow

val temperatureFlow: Flow = flow {
    emit(20)
    emit(21)
    emit(22)
    emit(23)
    emit(24)
}

val updateCount: Int = 5

suspend fun printTemperatures() {
    # Your code here
}

Need a hint?

Use for (temperature in temperatureFlow) inside the suspend function to get each value.

4

Run the program and see the output

Write a main function using runBlocking to call printTemperatures(). This will print all temperature updates one by one.

Kotlin

import kotlinx.coroutines.runBlocking

fun main() = runBlocking {
    # Your code here
}

Need a hint?

Use runBlocking to call the suspend function from main.