未调用http响应上的RxJs / Angular2映射函数

Question

Ok, there must be something I don't understand regarding the map() function. I'd expect that in both cases of the subscription the term mapped is written to the console. However, it is not if the http response has a status code of 4xx.

http.get("http://my.domain/rest/path").map(
  data => {
    console.log("mapped");
    return data;
  }
).subscribe(
  data => {
    console.log("good");
  },
  error => {
    console.log("bad");
  }
);

Any hints here?

Answer 1

map function only proceeds 'good' data and not error. In real case, I'd expect different body data for Ok cases (real data) and Bad Request cases (error messages) too. To catch and handle error in http.get function, use catch :

let obs = http.get("http://my.domain/rest/path").map(
  data => {
    console.log("mapped");
    return data;
  }
).catch(err => console.log(err));

obs.subscribe(...);

Answer 2

The Angular 2 Http client treats responses with 4xx and 5xx status codes as errors . So the map operator does not receive an emitted response.

Note that if an error is thrown due to the response's status code, the error will contain status and statusText properties:

http.get("http://my.domain/rest/path").map(
  data => {
    console.log("mapped");
    return data;
  }
).subscribe(
  data => {
    console.log("good");
  },
  error => {
    if (error.status) {
      console.log("somewhat bad: " + error.status);
    } else {
      console.log("really bad");
    }
  }
);