Operator之多重订阅(Working with multiple subscribers)

多重订阅：一个生成者，多个消费者

multicast

let publisher = ["First", "Second", "Third"]
    .publisher
    .map {
        ($0, Int.random(in: 1...100))
    }
    .print("Random")
    .multicast {
        PassthroughSubject<(String, Int), Never>()
    }

cancellable1 = publisher.sink { print($0) }
cancellable2 = publisher.sink { print($0) }
cancellable3 = publisher.sink { print($0) }

publisher.connect()

打印结果如下：

Random: receive value: (("First", 22))
("First", 22)
("First", 22)
("First", 22)
Random: receive value: (("Second", 82))
("Second", 82)
("Second", 82)
("Second", 82)
Random: receive value: (("Third", 59))
("Third", 59)
("Third", 59)
("Third", 59)

share可自动连接，不需要调用.connect

let publisher = ["First", "Second", "Third"]
    .publisher
    .map {
        ($0, Int.random(in: 1...100))
    }
    .print("Random")
    .share()

cancellable1 = publisher.sink { print($0) }
cancellable2 = publisher.sink { print($0) }
cancellable3 = publisher.sink { print($0) }

share是下边代码的极简写法：

.multicast { PassthroughSubject<(String, Int), Never>() }

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