Question

这段代码解析三元组（不那么重要）并且应该一次返回一个停车位。问题是调用observer.next（）会打破循环，因为它只运行一次。 console.log也没有被调用。我可能遗漏了一些东西但是有可能是observer.next（）打破了循环吗？是否有错误或是一个功能还是我错了？

 return Observable.create(observer => {
  this.fetch.get(datasetUrl).then(response => {
    // Get all subjects that are parkings
    const parkingTriples = [],
      parkings = [],
      totalspacesParking = [],
      labels = [];
    for (let index = 0; index < response.triples.length; index++) {
      if (response.triples[index].object === 'http://vocab.datex.org/terms#UrbanParkingSite') {
        parkingTriples.push(response.triples[index]);
      }
      if (response.triples[index].predicate === 'http://vocab.datex.org/terms#parkingNumberOfSpaces') {
        totalspacesParking.push(response.triples[index]);
      }
      if (response.triples[index].predicate === 'http://www.w3.org/2000/01/rdf-schema#label') {
        labels.push(response.triples[index]);
      }
    }
    const _parkings = [];
    for (let index = 0; index < parkingTriples.length; index++) {
      const totalspacesresult = find(totalspacesParking, (o) => {
        return o.subject === parkingTriples[index].subject
      });
      const totalspaces = parseInt(n3.Util.getLiteralValue(totalspacesresult.object), 10);
      const labelresult = find(labels, (o) => {
        return o.subject === parkingTriples[index].subject
      });
      const rdfslabel = n3.Util.getLiteralValue(labelresult.object);
      const id = rdfslabel.replace(' ', '-').toLowerCase();
      observer.next(new Parking(rdfslabel, parkingTriples[index].subject, id, totalspaces, datasetUrl));
      console.log(observer);
    }

  })
})

Answer 1

通常，Subject不会破坏您的代码。鉴于以下内容：

＆＃13;

const observer = new Rx.Subject();
const parkingTriples = new Array(10);

observer.subscribe(val => console.log('value emitted: ' + val));

for (let index = 0; index < parkingTriples.length; index++) {
  observer.next(index); 
  console.log('I still get hit through'); 
}

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/5.4.2/Rx.js"></script>

＆＃13;

每次都会发出I still get hit through。最有可能的是observer未在您的代码中定义，因此调用observer.next()中断并且永远不会看到以下console.log。

Answer 2

鉴于您更新的代码我建议调试它。很可能这个bug不在Rx位中。我重构了你的代码，以便在Rx逻辑和响应解析之间进行分割：

function getParkings(datasetUrl){
  return Rx.Observable.defer(() => this.fetch.get(datasetUrl))
    .mergeMap(response => parseParkingResponse(response));
}

function parseParkingResponse(response) {
  const parkingTriples = [],
    parkings = [],
    totalspacesParking = [],
    labels = [];
  for (let index = 0; index < response.triples.length; index++) {
    if (response.triples[index].object === 'http://vocab.datex.org/terms#UrbanParkingSite') {
      parkingTriples.push(response.triples[index]);
    }
    if (response.triples[index].predicate === 'http://vocab.datex.org/terms#parkingNumberOfSpaces') {
      totalspacesParking.push(response.triples[index]);
    }
    if (response.triples[index].predicate === 'http://www.w3.org/2000/01/rdf-schema#label') {
      labels.push(response.triples[index]);
    }
  }

  const _parkings = [];
  for (let index = 0; index < parkingTriples.length; index++) {
    const totalspacesresult = find(totalspacesParking, (o) => {
      return o.subject === parkingTriples[index].subject
    });
    const totalspaces = parseInt(n3.Util.getLiteralValue(totalspacesresult.object), 10);
    const labelresult = find(labels, (o) => {
      return o.subject === parkingTriples[index].subject
    });
    const rdfslabel = n3.Util.getLiteralValue(labelresult.object);
    const id = rdfslabel.replace(' ', '-').toLowerCase();
    _parkings.push(new Parking(rdfslabel, parkingTriples[index].subject, id, totalspaces, datasetUrl));
  }

  return _parkings;
}

这样可以更容易地调试正在进行的操作。

Observable.next（）打破了循环

2 个答案: