rxjs 中 do 和 subscribe 的区别

Question

在这个 JS Bin 中，我有一些加载模拟分页数据源的可观察对象。 getPageFromServer 从给定索引开始的服务器加载一页数据：

function getPageFromServer( index ) {

  index = index || 0;

  var values = [];
  var nextIndex;

  for(var i = 0; i< 3; i++) {
    var newValue = index + i;
    if(newValue < 10){
      values.push( newValue );
      nextIndex = newValue + 1;
    }
    else {
      nextIndex = undefined;
    }
  }

  data = { values: values, nextIndex: nextIndex };

  return Rx.Observable.return(data).delay(500);
}

getPagedItems 然后加载页面并将多个 observable 合并为一个，这样我们就可以获得所有页面的所有值的 observable：

function getPagedItems(index) {
  return getPageFromServer(index)
    .flatMap(function (response) {
      var result = Rx.Observable.from(response.values);

      if(response.nextIndex !== undefined){
        return result.concat( getPagedItems(response.nextIndex) );
      } else {
        return result;
      }

  });
}

这给了我预期的结果：

"page received: 1"
"page received: 2"
"page received: 3"
"page received: 4"
"page received: 5"
"page received: 6"
"page received: 7"
"page received: 8"
"page received: 9"
"complete"

但是，如果我在 getPagedItems 的末尾添加一个 do:

function getPagedItems(index) {
  return getPageFromServer(index)
    .flatMap(function (response) {
      var result = Rx.Observable.from(response.values);

      if(response.nextIndex !== undefined){
        return result.concat( getPagedItems(response.nextIndex) );
      } else {
        return result;
      }
  })
  .do( function ( result) { console.log( "do: " + result); } );
}

我得到每个值的次数等于我们在平面图中创建的可观察对象的数量：

"starting..."
"do: 0"
"page received: 0"
"do: 1"
"page received: 1"
"do: 2"
"page received: 2"
"do: 3"
"do: 3"
"page received: 3"
"do: 4"
"do: 4"
"page received: 4"
"do: 5"
"do: 5"
"page received: 5"
"do: 6"
"do: 6"
"do: 6"
"page received: 6"
"do: 7"
"do: 7"
"do: 7"
"page received: 7"
"do: 8"
"do: 8"
"do: 8"
"page received: 8"
"do: 9"
"do: 9"
"do: 9"
"do: 9"
"page received: 9"
"complete"

请向我解释为什么 "do" 触发了多次，而订阅中的 "onNext" 只触发了一次。

非常感谢

Answer 1

我在发布问题后大约 5 分钟找到了这个答案！

do 多次触发的原因是因为我正在递归调用 loadCommentThreads，所以每个对 loadComment 线程的嵌套调用在消息 returns 到父调用函数实例之前的管道中都有一个 do。

rxjs 中 do 和 subscribe 的区别

Difference between do and subscribe in rxjs

javascript

rxjs

typescript