done lecture 11

src/main/java/com/rxmobileteam/lecture11/Riddle1.kt

@@ -11,7 +11,7 @@ object Riddle1 {
    */
   fun solve(value: Int): Observable<Int> {
     // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Observable.just(value)
   }
 }
 

src/main/java/com/rxmobileteam/lecture11/Riddle10.kt

@@ -9,8 +9,13 @@ object Riddle10 {
    *
    * Use case: Get some user data and perform a network request with the user data and have both data accessible afterwards.
    */
-  fun solve(first: Observable<Int>, function: (Int) -> Observable<String>): Observable<Pair<Int, String>> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+  fun solve(
+    first: Observable<Int>,
+    function: (Int) -> Observable<String>
+  ): Observable<Pair<Int, String>> {
+    return first.flatMap(
+      { value -> function(value) },
+      { value: Int, functionResult: String -> Pair(value, functionResult) }
+    )
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle11.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import java.util.concurrent.TimeUnit
 
 object Riddle11 {
   /**
@@ -10,7 +11,6 @@ object Riddle11 {
    * Use case: Handle the click of a button right away but prevent double clicking by not handling multiple click events within a given time window.
    */
   fun solve(source: Observable<Unit>): Observable<Unit> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.throttleFirst(300L, TimeUnit.MILLISECONDS)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle12.kt

@@ -10,7 +10,6 @@ object Riddle12 {
    * Use case: Getting a network error and you want to recover and show some default state.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.onErrorReturnItem(5)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle13.kt

@@ -10,7 +10,6 @@ object Riddle13 {
    * Use case: You only want to observe changes of a value but don't care if the same value has been emitted consecutively.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.distinctUntilChanged()
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle14.kt

@@ -10,7 +10,6 @@ object Riddle14 {
    * Use case: Retry an operation for a number of times or until a valid error occurred.
    */
   fun solve(source: Single<Unit>): Single<Unit> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.retry(2) { t -> t !is IllegalArgumentException }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle15.kt

@@ -10,7 +10,6 @@ object Riddle15 {
    * Use case: You have two sources of your data (cache & network request). You want to subscribe to both right away and keep the emission order.
    */
   fun solve(first: Observable<Int>, second: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Observable.concatEager(listOf(first, second))
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle16.kt

@@ -12,7 +12,8 @@ object Riddle16 {
    * Use case: The [source] Observable is a TextField and you want to issue a network request while disposing the old requests in case the user has typed something new.
    */
   fun solve(source: Observable<String>, function: (String) -> Single<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.switchMapSingle {
+      function(it)
+    }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle17.kt

@@ -10,7 +10,6 @@ object Riddle17 {
    * Use case: Reactive types are lazy by default. Hence, you might also want to get the value upon the subscription and not execution time.
    */
   fun solve(function: () -> Int): Single<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Single.fromSupplier(function)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle18.kt

@@ -10,7 +10,6 @@ object Riddle18 {
    * Use case: You have multiple sources and want to get the data from either one and then be consistent and not switch between multiple sources.
    */
   fun solve(first: Observable<Int>, second: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Observable.amb(listOf(first, second))
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle19.kt

@@ -11,8 +11,9 @@ object Riddle19 {
    * Use case: Transform any listener into an Observable.
    */
   fun solve(interaction: Interaction): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Observable.create { emitter ->
+      interaction.listener = emitter::onNext
+    }
   }
 
   interface Interaction {

src/main/java/com/rxmobileteam/lecture11/Riddle2.kt

@@ -10,7 +10,6 @@ object Riddle2 {
    * Use case: You want to transform the data.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.map { it + 1 }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle20.kt

@@ -10,7 +10,6 @@ object Riddle20 {
    * Use case: There something you want to execute and in your UI you have multiple trigger points.
    */
   fun solve(first: Observable<Int>, second: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return first.mergeWith(second)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle21.kt

@@ -10,7 +10,6 @@ object Riddle21 {
    * Use case: Sometimes you can't do everything reactively and need to break out of it.
    */
   fun solve(source: Observable<Int>): Int {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.blockingFirst()
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle22.kt

@@ -10,7 +10,6 @@ object Riddle22 {
    * Use case: Group related data while skipping over some of it.
    */
   fun solve(source: Observable<Int>): Observable<List<Int>> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.buffer(2, 3)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle23.kt

@@ -10,7 +10,6 @@ object Riddle23 {
    * Use case: You get some data from a bad source and know for sure it's of a certain type that you require.
    */
   fun solve(source: Observable<Any>): Observable<String> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.map { it as String }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle24.kt

@@ -11,7 +11,6 @@ object Riddle24 {
    * Use case: Know how many emissions have been sent out.
    */
   fun solve(source: Observable<Any>): Single<Long> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.count()
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle25.kt

@@ -10,7 +10,6 @@ object Riddle25 {
    * Use case: Continue with data if the stream is empty.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.defaultIfEmpty(5)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle26.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import java.util.concurrent.TimeUnit
 
 object Riddle26 {
   /**
@@ -10,7 +11,6 @@ object Riddle26 {
    * Use case: Delay emission of events to simulate some indication.
    */
   fun solve(source: Observable<Long>): Observable<Long> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.delay(300, TimeUnit.MILLISECONDS)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle27.kt

@@ -10,7 +10,6 @@ object Riddle27 {
    * Use case: Add some logging.
    */
   fun solve(source: Observable<Long>, function: (Long) -> Unit): Observable<Long> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.doOnNext(function)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle28.kt

@@ -10,7 +10,6 @@ object Riddle28 {
    * Use case: Add some logging.
    */
   fun solve(source: Completable, function: () -> Unit): Completable {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.doOnComplete(function)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle29.kt

@@ -10,7 +10,6 @@ object Riddle29 {
    * Use case: Add some logging.
    */
   fun solve(source: Maybe<Int>, function: (Throwable) -> Unit): Maybe<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.doOnError(function)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle3.kt

@@ -10,7 +10,6 @@ object Riddle3 {
    * Use case: You want to filter certain items out.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.filter { it % 2 == 0 }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle30.kt

@@ -10,7 +10,6 @@ object Riddle30 {
    * Use case: Add some logging.
    */
   fun solve(source: Single<Int>, function: () -> Unit): Single<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.doOnSubscribe { function.invoke() }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle31.kt

@@ -10,7 +10,6 @@ object Riddle31 {
    * Use case: You want to re-run a certain Observable a number of times.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.repeat(3)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle32.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Single
+import java.util.concurrent.TimeUnit
 import java.util.concurrent.TimeoutException
 
 object Riddle32 {
@@ -11,7 +12,6 @@ object Riddle32 {
    * Use case: You want to terminate the given reactive type and stop the operation.
    */
   fun solve(source: Single<Long>): Single<Long> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.timeout(3, TimeUnit.SECONDS)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle33.kt

@@ -11,7 +11,6 @@ object Riddle33 {
    * Use case: You want to shift work to a particular [Scheduler].
    */
   fun solve(source: Completable, scheduler: Scheduler): Completable {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.observeOn(scheduler)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle34.kt

@@ -11,7 +11,6 @@ object Riddle34 {
    * Use case: You want to shift work to a particular [Scheduler].
    */
   fun solve(source: Completable, scheduler: Scheduler): Completable {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.subscribeOn(scheduler)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle35.kt

@@ -11,7 +11,6 @@ object Riddle35 {
    * Use case: You have a local cache and only want to hit the network if the cache misses.
    */
   fun solve(first: Maybe<String>, second: Single<String>): Single<String> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return first.switchIfEmpty(second)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle36.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import java.util.concurrent.TimeUnit
 
 object Riddle36 {
   /**
@@ -10,7 +11,6 @@ object Riddle36 {
    * Use case: You want the user-input to trigger a search request for the entered text but only when no changes have been made for a pre-determined time to avoid unnecessary requests.
    */
   fun solve(source: Observable<String>, milliseconds: Long): Observable<String> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.debounce(milliseconds, TimeUnit.MILLISECONDS)
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle37.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import java.io.IOException
 
 object Riddle37 {
   /**
@@ -10,7 +11,11 @@ object Riddle37 {
    * Use case: You want to recover from an expected error and map them to a particular result.
    */
   fun solve(source: Observable<Boolean>): Observable<Boolean> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.onErrorResumeNext {
+      when (it) {
+        is IOException -> Observable.just(false)
+        else -> Observable.error(it)
+      }
+    }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle4.kt

@@ -11,7 +11,6 @@ object Riddle4 {
    * Use case: Some button that can toggle two states. For instance a switch between White & Dark theme.
    */
   fun solve(source: Observable<Unit>): Observable<Boolean> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.scan(false) { acc, _ -> !acc }
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle5.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.functions.BiFunction
 
 object Riddle5 {
   /**
@@ -10,7 +11,6 @@ object Riddle5 {
    * Use case: Two input fields in a calculator that need to be summed up and the result should be updated every time one of the inputs change.
    */
   fun solve(first: Observable<Int>, second: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Observable.combineLatest(first, second, { a, b -> a + b })
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle6.kt

@@ -12,7 +12,6 @@ object Riddle6 {
    * Use case: Execute two network requests in parallel and wait for each other and process the combined data.
    */
   fun solve(first: Single<Int>, second: Single<Int>): Single<Pair<Int, Int>> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return Single.zip(first, second, { a, b -> a to b })
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle7.kt

@@ -10,7 +10,6 @@ object Riddle7 {
    * Use case: You never want to show the same value twice.
    */
   fun solve(source: Observable<Int>): Observable<Int> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.distinct()
   }
 }

src/main/java/com/rxmobileteam/lecture11/Riddle8.kt

@@ -2,6 +2,7 @@ package com.rxmobileteam.lecture11
 
 import com.rxmobileteam.utils.ExerciseNotCompletedException
 import io.reactivex.rxjava3.core.Observable
+import java.util.concurrent.TimeUnit
 
 object Riddle8 {
   /**
@@ -10,7 +11,6 @@ object Riddle8 {
    * Use case: Make an Observable "lazy" for some time. For instance, when wanting to postpone some UI action.
    */
   fun solve(source: Observable<Unit>): Observable<Unit> {
-    // TODO: implement this method
-    throw ExerciseNotCompletedException()
+    return source.delaySubscription(200, TimeUnit.MILLISECONDS)
   }
 }