# PublishSubject

![](/files/-MWlwI14ihu6EL0qd8RT)

**PublishSubject** 将对观察者发送订阅后产生的元素，而在订阅前发出的元素将不会发送给观察者。如果你希望观察者接收到所有的元素，你可以通过使用 `Observable` 的 `create` 方法来创建 `Observable`，或者使用 [ReplaySubject](/rxswift/rxswift_core/observable_and_observer/replay_subject.md)。

![](/files/-MWlwI16eSKUJGKcQ0hE)

如果源 `Observable` 因为产生了一个 `error` 事件而中止， **PublishSubject** 就不会发出任何元素，而是将这个 `error` 事件发送出来。

## 演示

```swift
let disposeBag = DisposeBag()
let subject = PublishSubject<String>()

subject
  .subscribe { print("Subscription: 1 Event:", $0) }
  .disposed(by: disposeBag)

subject.onNext("🐶")
subject.onNext("🐱")

subject
  .subscribe { print("Subscription: 2 Event:", $0) }
  .disposed(by: disposeBag)

subject.onNext("🅰️")
subject.onNext("🅱️")
```

**输出结果：**

```swift
Subscription: 1 Event: next(🐶)
Subscription: 1 Event: next(🐱)
Subscription: 1 Event: next(🅰️)
Subscription: 2 Event: next(🅰️)
Subscription: 1 Event: next(🅱️)
Subscription: 2 Event: next(🅱️)
```


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