发出传递函数返回的值的单个

方法#fromCallable是一个工厂,每次都会返回一个新的。每次订阅你都会订阅一首新的单曲。因此,将为每个订阅者调用该函数。如果要缓存该值,可以使用#cache运算符。请看提供的两个测试。

测试“notCached”将为每个订阅调用该函数。测试“缓存”将只调用函数一次。如果您想共享结果,只需使用create Single#fromCallable with#cache操作符。

环境

dependencies {
compile 'io.reactivex.rxjava2:rxjava:2.1.6'
compile 'org.mockito:mockito-core:2.11.0'
testCompile("org.junit.jupiter:junit-jupiter-api:5.0.0")
testRuntime("org.junit.jupiter:junit-jupiter-engine:5.0.0")

测验

@Test
void notCached() throws Exception {
    Callable<Integer> mock = mock(Callable.class);

    when(mock.call()).thenReturn(10);

    Single<Integer> integerSingle = Single.fromCallable(mock);

    Disposable subscribe1 = integerSingle.subscribe();
    Disposable subscribe2 = integerSingle.subscribe();

    verify(mock, times(2)).call();
}

@Test
void cached() throws Exception {
    Callable<Integer> mock = mock(Callable.class);

    when(mock.call()).thenReturn(10);

    Single<Integer> integerSingle = Single.fromCallable(mock).cache();

    Disposable subscribe1 = integerSingle.subscribe();
    Disposable subscribe2 = integerSingle.subscribe();
    Disposable subscribe3 = integerSingle.subscribe();
    Disposable subscribe4 = integerSingle.subscribe();

    verify(mock, times(1)).call();
}