通常而言，Rx如果遇到if条件语句、switch case语句时需要先选择分支条件，然后再进行链式调用。RxCondition产生的目的就是为了在这些情况下也能顺利地使用链式调用。
我在查找RxJava的条件、布尔操作符时，没有找到符合我需求的操作符。于是，我在网上找到了RxJavaComputationExpressions， 做了一些修改将RxJava1升级到RxJava2，增加了对Flowable、Maybe、Single、Completable的支持。
对于Android项目，Android Studio默认使用jcenter。
对于Java项目如果使用gradle构建，由于默认不是使用jcenter，需要在相应module的build.gradle中配置
repositories {
mavenCentral()
jcenter()
}Gradle:
compile 'tony-common:rxconditions:1.1.0'Maven:
<dependency>
<groupId>tony-common</groupId>
<artifactId>rxconditions</artifactId>
<version>1.1.0</version>
<type>pom</type>
</dependency>if条件语句传统的写法：
Observable<String> observable = null;
if (flag) {
observable = Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
e.onNext("this is true");
}
});
} else {
observable = Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
e.onNext("this is false");
}
});
}
observable.subscribe(new Consumer<String>() {
@Override
public void accept(@NonNull String s) throws Exception {
System.out.println("s=" s);
}
});使用了ifThen()以后的写法：
Statement.ifThen(new BooleanSupplier() {
@Override
public boolean getAsBoolean() throws Exception {
return flag;
}
}, Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
e.onNext("this is true");
}
}),Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
e.onNext("this is false");
}
})).subscribe(new Consumer<String>() {
@Override
public void accept(@NonNull String s) throws Exception {
System.out.println("s=" s);
}
});ifThen(BooleanSupplier condition, Observable<? extends R> then,Observable<? extends R> orElse)，其中第一个Observable是条件为true时执行的，第二个Observable则是条件为false时执行。
使用lambda表达式，进一步简化写法：
Statement.ifThen(()->{
return flag;
},Observable.create((e)->{
e.onNext("this is true");
}),Observable.create((e)->{
e.onNext("this is false");
})).subscribe((Consume) (s) -> {System.out.println("s=" s)});当然，ifThen也支持Flowable：
Statement.ifThen(()->{
return flag;
},Flowable.just("this is true"), Flowable.just("this is false"))
.subscribe((Consume) (s) -> {System.out.println("s=" s)});switch case语句传统的写法：
Flowable<String> flowable = null;
switch(type) {
case 0:
flowable = Flowable.just("this is 0");
break;
case 1:
flowable = Flowable.just("this is 1");
break;
case 2:
flowable = Flowable.just("this is 2");
break;
case 3:
flowable = Flowable.just("this is 3");
break;
default:
flowable = Flowable.just("this is default");
break;
}
flowable.subscribe(new Consumer<String>() {
@Override
public void accept(@NonNull String s) throws Exception {
System.out.println("s=" s);
}
});使用了switchCase()以后的写法：
Map<Integer,Flowable<String>> maps = new HashMap<>();
maps.put(0,Flowable.just("this is 0"));
maps.put(1,Flowable.just("this is 1"));
maps.put(2,Flowable.just("this is 2"));
maps.put(3,Flowable.just("this is 3"));
Statement.switchCase(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
return type;
}
},maps,Flowable.just("this is default"))
.subscribe(new Consumer<String>() {
@Override
public void accept(@NonNull String s) throws Exception {
System.out.println("s=" s);
}
});首先，将各个分支情况放入maps中。 其次，switchCase()的第一个参数是caseSelector，用于返回maps的key。最后一个参数是defaultCase，相当于switch case语句中的default语句。
改成lambda表达：
Map<Integer,Flowable<String>> maps = new HashMap<>();
maps.put(0,Flowable.just("this is 0"));
maps.put(1,Flowable.just("this is 1"));
maps.put(2,Flowable.just("this is 2"));
maps.put(3,Flowable.just("this is 3"));
Statement.switchCase((Callable)()-> {return type;},maps,Flowable.just("this is default"))
.subscribe((Consumer)(s) -> {System.out.println("s=" s);});switchCase()中，第一个参数返回的是Map<K, R>中的key，它支持范型，所以switchCase()相对于switch case语句而已能够支持更多种类型。
Copyright (C) 2017 Tony Shen.
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