150: Learning Kotlin – Returns, Jumps & Labels

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Code

data class Customer(val isPlatinum: Boolean)

fun main() {

    val customer = Customer(false)

    println("Number of points customer has: ${calculatePoints(customer)}")

    // Break out of the loop once we're over 25
    for (i in 1..100) {
        if (i > 25) {
            break
        } else {
            println(i)
        }
    }


    // Skip all even numbers
    for (i in 1..100) {
        if (i % 2 == 0) {
            continue
        } else {
            println(i)
        }
    }


    // Break out of the outer loop (which breaks out of the inner too) using a label
    [email protected] for (i in 1..100) {
        for (j in 100..200) {
            if (j > 150) [email protected] // This will break out of the inner loop and outer loop
            else println("i: $i, j: $j")
        }
    }

    // Continue processing the next outer loop value when a condition is met.
    [email protected] for (i in 1..100) {
        for (j in 100..200) {
            if (j > 150) [email protected] // This will break out of the inner loop and outer loop
            else println("i: $i, j: $j")
        }
    }

    // returns with label
    example1()
    example2()

    println("I'm done processing!")
}

fun calculatePoints(customer: Customer): Int {
    if (customer.isPlatinum) {
        return 100000
    } else {
        return 10
    }
}


fun example1() {
    listOf(1, 2, 3, 4, 5, 6, 7, 8, 9).forEach {
        if (it > 7) {
            return
        } else {
            println(it)
        }
    }
    println("This wont print :( because return exited the bar() function")
}

fun example2() {
    listOf(1, 2, 3, 4, 5, 6, 7, 8, 9).forEach [email protected] {
        if (it > 7) {
            [email protected]
        } else {
            println(it)
        }
    }
    println("This will print! :) return exited the forEach!")
}

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147: Disposing RxJava 2 Streams with AutoDispose

In this short fragment episode, Donn explains how you can clean up your RxJava 2 streams and ensure no memory leaks are occurring by using the AutoDispose library from Uber.

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Code Samples

Java

myObservable
    .map(...)
    .as(AutoDispose.<SomeType>autoDisposable(AndroidLifecycleScopeProvider.from(this)))
    .subscribe(...)

Kotlin

myObservable
    .map(...)
    .autoDisposable(AndroidLifcycleScopeProvider.from(this))
    .subscribe(...)

With Scope Event Provided

myObservable
    .map(...)
    .autoDisposable(AndroidLifcycleScopeProvider.from(this, Lifecycle.Event.ON_DESTROY))
    .subscribe(...)

Testing

// File: CustomerService.kt
class CustomerService @Inject constructor(...) {
    lateinit var scopeProvider: ScopeProvider
}

// Usage in Fragment/Activity/etc
val service = CustomerService(...).apply {
    scopeProvider = AndroidLifecycleScopeProvider.from(this)
}

// Usage in Test
val service = CustomerService(...).apply {
    scopeProvider = TestScopeProvider.create()
}

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146: 3 Things Every Android Developer Needs to Know

In this episode of Fragmented, Donn digs into three things that every Android developer needs to know.

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  • Dependency Injection

    1. Constructor_setter_method injection
    2. Service Locators or other DI frameworks
    3. Common Frameworks
      1. Dagger
      2. Koin
      3. Kodein
      4. ToothPick
  • How to test

    1. Functional / System
    2. Integration
    3. Unit
    4. Tools:
      1. jUnit
      2. Espresso
      3. Spek
  • Keep it simple simple

    1. KISS principle KISS principle – Wikipedia
    2. Examples
      1. Code Duplication
        1. “Extract this into a method”
      2. Lets create a framework for this
      3. Kaushik’s – 3x rule
        • if something is duplicated 3 or more times, think about extracting it
      4. 3/6 Rule – In 6 months, will I be able to understand this in under 3 minutes?

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145: Tracking Network Requests With x-Request-ID

In this short fragment, Kaushik explains how you can trace network requests from your app by adding a special header. Easily trace an HTTP request all the way from a client to your backend web process.

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143: Real world testing thoughts

In this mini fragment, Donn and Kaushik share some thoughts on real world testing with Android development – a favorite topic of theirs.

Kaushik recently ran into a case where an espresso test fails because the UI stops performing. It’s an interesting discussion on figuring out what matters when you write your tests. They dive into strategies and techniques around testing. What makes a good test, what should you be testing?

They then talk about why Hermetic testing is pretty hard on mobile and ideas around a simple solution that could be provided out of the box. They then round it up talking about TDD and it’s role in today’s world.

Hope you enjoy this one!

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