Merge pull request #714 from benjchristensen/rxjava-computation-expre…

…ssions

rxjava-computation-expressions

rxjava-contrib/rxjava-computation-expressions/build.gradle

@@ -0,0 +1,20 @@
+apply plugin: 'osgi'
+
+sourceCompatibility = JavaVersion.VERSION_1_6
+targetCompatibility = JavaVersion.VERSION_1_6
+
+dependencies {
+    compile project(':rxjava-core')
+    testCompile project(":rxjava-core").sourceSets.test.output 
+    provided 'junit:junit-dep:4.10'
+    provided 'org.mockito:mockito-core:1.8.5'
+}
+
+jar {
+    manifest {
+        name = 'rxjava-computation-expressions'
+        instruction 'Bundle-Vendor', 'Netflix'
+        instruction 'Bundle-DocURL', 'https://github.com/Netflix/RxJava'
+        instruction 'Import-Package', '!org.junit,!junit.framework,!org.mockito.*,*'
+    }
+}

rxjava-contrib/rxjava-computation-expressions/src/main/java/rx/Statement.java

@@ -0,0 +1,191 @@
+package rx;
+
+import java.util.Map;
+
+import rx.operators.OperationConditionals;
+import rx.util.functions.Func0;
+
+/**
+ * Imperative statements expressed as Observable operators.
+ */
+public class Statement {
+
+    /**
+     * Return a particular one of several possible Observables based on a case
+     * selector.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/switchCase.png">
+     * 
+     * @param <K>
+     *            the case key type
+     * @param <R>
+     *            the result value type
+     * @param caseSelector
+     *            the function that produces a case key when an
+     *            Observer subscribes
+     * @param mapOfCases
+     *            a map that maps a case key to an Observable
+     * @return a particular Observable chosen by key from the map of
+     *         Observables, or an empty Observable if no Observable matches the
+     *         key
+     */
+    public static <K, R> Observable<R> switchCase(Func0<? extends K> caseSelector,
+            Map<? super K, ? extends Observable<? extends R>> mapOfCases) {
+        return switchCase(caseSelector, mapOfCases, Observable.<R> empty());
+    }
+
+    /**
+     * Return a particular one of several possible Observables based on a case
+     * selector and run it on the designated scheduler.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/switchCase.s.png">
+     * 
+     * @param <K>
+     *            the case key type
+     * @param <R>
+     *            the result value type
+     * @param caseSelector
+     *            the function that produces a case key when an
+     *            Observer subscribes
+     * @param mapOfCases
+     *            a map that maps a case key to an Observable
+     * @param scheduler
+     *            the scheduler where the empty observable is observed
+     * @return a particular Observable chosen by key from the map of
+     *         Observables, or an empty Observable if no Observable matches the
+     *         key, but one that runs on the designated scheduler in either case
+     */
+    public static <K, R> Observable<R> switchCase(Func0<? extends K> caseSelector,
+            Map<? super K, ? extends Observable<? extends R>> mapOfCases, Scheduler scheduler) {
+        return switchCase(caseSelector, mapOfCases, Observable.<R> empty(scheduler));
+    }
+
+    /**
+     * Return a particular one of several possible Observables based on a case
+     * selector, or a default Observable if the case selector does not map to
+     * a particular one.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/switchCase.png">
+     * 
+     * @param <K>
+     *            the case key type
+     * @param <R>
+     *            the result value type
+     * @param caseSelector
+     *            the function that produces a case key when an
+     *            Observer subscribes
+     * @param mapOfCases
+     *            a map that maps a case key to an Observable
+     * @param defaultCase
+     *            the default Observable if the {@code mapOfCases} doesn't contain a value for the key returned by the {@case caseSelector}
+     * @return a particular Observable chosen by key from the map of
+     *         Observables, or the default case if no Observable matches the key
+     */
+    public static <K, R> Observable<R> switchCase(Func0<? extends K> caseSelector,
+            Map<? super K, ? extends Observable<? extends R>> mapOfCases,
+            Observable<? extends R> defaultCase) {
+        return Observable.create(OperationConditionals.switchCase(caseSelector, mapOfCases, defaultCase));
+    }
+
+    /**
+     * Return an Observable that replays the emissions from the source
+     * Observable, and then continues to replay them so long as a condtion is
+     * true.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/doWhile.png">
+     * 
+     * @param postCondition
+     *            the post condition to test after the source
+     *            Observable completes
+     * @return an Observable that replays the emissions from the source
+     *         Observable, and then continues to replay them so long as the post
+     *         condition is true
+     */
+    public static <T> Observable<T> doWhile(Observable<T> source, Func0<Boolean> postCondition) {
+        return Observable.create(OperationConditionals.doWhile(source, postCondition));
+    }
+
+    /**
+     * Return an Observable that replays the emissions from the source
+     * Observable so long as a condtion is true.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/whileDo.png">
+     * 
+     * @param preCondition
+     *            the condition to evaluate before subscribing to or
+     *            replaying the source Observable
+     * @return an Observable that replays the emissions from the source
+     *         Observable so long as <code>preCondition</code> is true
+     */
+    public static <T> Observable<T> whileDo(Observable<T> source, Func0<Boolean> preCondition) {
+        return Observable.create(OperationConditionals.whileDo(source, preCondition));
+    }
+
+    /**
+     * Return an Observable that emits the emissions from a specified Observable
+     * if a condition evaluates to true, otherwise return an empty Observable.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/ifThen.png">
+     * 
+     * @param <R>
+     *            the result value type
+     * @param condition
+     *            the condition that decides whether to emit the emissions
+     *            from the <code>then</code> Observable
+     * @param then
+     *            the Observable sequence to emit to if {@code condition} is {@code true}
+     * @return an Observable that mimics the {@code then} Observable if the {@code condition} function evaluates to true, or an empty
+     *         Observable otherwise
+     */
+    public static <R> Observable<R> ifThen(Func0<Boolean> condition, Observable<? extends R> then) {
+        return ifThen(condition, then, Observable.<R> empty());
+    }
+
+    /**
+     * Return an Observable that emits the emissions from a specified Observable
+     * if a condition evaluates to true, otherwise return an empty Observable
+     * that runs on a specified Scheduler.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/ifThen.s.png">
+     * 
+     * @param <R>
+     *            the result value type
+     * @param condition
+     *            the condition that decides whether to emit the emissions
+     *            from the <code>then</code> Observable
+     * @param then
+     *            the Observable sequence to emit to if {@code condition} is {@code true}
+     * @param scheduler
+     *            the Scheduler on which the empty Observable runs if the
+     *            in case the condition returns false
+     * @return an Observable that mimics the {@code then} Observable if the {@code condition} function evaluates to true, or an empty
+     *         Observable running on the specified Scheduler otherwise
+     */
+    public static <R> Observable<R> ifThen(Func0<Boolean> condition, Observable<? extends R> then, Scheduler scheduler) {
+        return ifThen(condition, then, Observable.<R> empty(scheduler));
+    }
+
+    /**
+     * Return an Observable that emits the emissions from one specified
+     * Observable if a condition evaluates to true, or from another specified
+     * Observable otherwise.
+     * <p>
+     * <img width="640" src="https://raw.github.com/wiki/Netflix/RxJava/images/rx-operators/ifThen.e.png">
+     * 
+     * @param <R>
+     *            the result value type
+     * @param condition
+     *            the condition that decides which Observable to emit the
+     *            emissions from
+     * @param then
+     *            the Observable sequence to emit to if {@code condition} is {@code true}
+     * @param orElse
+     *            the Observable sequence to emit to if {@code condition} is {@code false}
+     * @return an Observable that mimics either the {@code then} or {@code orElse} Observables depending on a condition function
+     */
+    public static <R> Observable<R> ifThen(Func0<Boolean> condition, Observable<? extends R> then,
+            Observable<? extends R> orElse) {
+        return Observable.create(OperationConditionals.ifThen(condition, then, orElse));
+    }
+
+}