我无法确定这是一个范围问题还是我如何设置我的观察点的问题，但也许你可以提供帮助。
首先，我的逻辑。我的总体目标是能够在发送一个http.get请求之前检查一些数据是否保存在本地。我想做的是返回本地保存的数据（如果存在的话），我认为我可以使这个返回一个observable，这样我就可以订阅这个函数的输出，无论它是否返回本地数据或远程数据。任何关于这种逻辑的想法都将受到赞赏！
我正在关注More来实现我自己的观察。我遇到了一个问题，我无法在我的getData函数中定义我的观察者。
Here is Cory's working demo - 您可以在日志中看到服务中的this._dataObserver未定义，而在Cory中则为@Component({
selector: 'my-app',
template: `
<landing-page></landing-page>
`,
providers: [DataService],
directives: [LandingPageComponent]
})
export class App {
constructor() { }
}
bootstrap(App, [HTTP_BINDINGS])
.catch(err => console.error(err));
。这就是造成我问题的原因。
以下是代码中的代码段：
App.ts
@Component({
selector: 'landing-page',
template : `
hello
`,
})
export class LandingPageComponent implements OnInit{
data : Observable<any[]>;
constructor(
private _dataService : DataService
) { }
ngOnInit() {
this.data = this._dataService.data$;
this._dataService.getData();
}
}
LandingPageComponent.ts
@Injectable()
export class DataService {
data$ : Observable<any[]>; // data stream
private _baseUrl: string;
private _dataObserver : Observer<any[]>;
private _dataStore : {
data : any[]
};
constructor (
private _http: Http
) {
this._baseUrl = 'http://56e05c3213da80110013eba3.mockapi.io/api';
this.data$ = new Observable(observer => this._todosObserver = observer).share();
this._dataStore = { data: [] };
}
/** **************
* Public functions
*****************/
getData () {
this._http.get(`${this._baseUrl}/todos`)
.map(data => data.json())
.subscribe( data => {
this._dataStore.data = data;
console.log(this._dataObserver); //<------ This is undefined for me!
this._dataObserver.next(this.data);
},
error => {
console.log('couldn\'t load data! ' + error );
});
}
}
的DataService
public class MockRestClient : RestClient
{
public TestServer TestServer { get; set; }
public MockRestClient(TestServer testServer)
{
TestServer = testServer;
}
public override IRestResponse Execute(IRestRequest request)
{
// TODO: Currently the test server is only doing GET requests via RestSharp
HttpResponseMessage response = null;
Parameter body = request.Parameters.FirstOrDefault(p => p.Type == ParameterType.RequestBody);
HttpContent content;
if (body != null)
{
object val = body.Value;
byte[] requestBodyBytes;
string requestBody;
if (val is byte[])
{
requestBodyBytes = (byte[]) val;
content = new ByteArrayContent(requestBodyBytes);
}
else
{
requestBody = Convert.ToString(body.Value);
content = new StringContent(requestBody);
}
}
else
content = new StringContent("");
string urladd = "";
IEnumerable<string> @params = from p in request.Parameters
where p.Type == ParameterType.GetOrPost && p.Value != null
select p.Name + "=" + p.Value;
if(!@params.IsNullOrEmpty())
urladd = "?" + String.Join("&", @params);
IEnumerable<HttpHeader> headers = from p in request.Parameters
where p.Type == ParameterType.HttpHeader
select new HttpHeader
{
Name = p.Name,
Value = Convert.ToString(p.Value)
};
foreach (HttpHeader header in headers)
{
content.Headers.Add(header.Name, header.Value);
}
content.Headers.ContentType.MediaType = "application/json";
switch (request.Method)
{
case Method.GET:
response = TestServer.HttpClient.GetAsync(request.Resource + urladd).Result;
break;
case Method.DELETE:
response = TestServer.HttpClient.DeleteAsync(request.Resource + urladd).Result;
break;
case Method.POST:
response = TestServer.HttpClient.PostAsync(request.Resource + urladd, content).Result;
break;
case Method.PUT:
response = TestServer.HttpClient.PutAsync(request.Resource + urladd, content).Result;
break;
default:
return null;
}
var restResponse = ConvertToRestResponse(request, response);
return restResponse;
}
private static RestResponse ConvertToRestResponse(IRestRequest request, HttpResponseMessage httpResponse)
{
RestResponse restResponse1 = new RestResponse();
restResponse1.Content = httpResponse.Content.ReadAsStringAsync().Result;
restResponse1.ContentEncoding = httpResponse.Content.Headers.ContentEncoding.FirstOrDefault();
restResponse1.ContentLength = (long)httpResponse.Content.Headers.ContentLength;
restResponse1.ContentType = httpResponse.Content.Headers.ContentType.ToString();
if (httpResponse.IsSuccessStatusCode == false)
{
restResponse1.ErrorException = new HttpRequestException();
restResponse1.ErrorMessage = httpResponse.Content.ToString();
restResponse1.ResponseStatus = ResponseStatus.Error;
}
restResponse1.RawBytes = httpResponse.Content.ReadAsByteArrayAsync().Result;
restResponse1.ResponseUri = httpResponse.Headers.Location;
restResponse1.Server = "http://localhost";
restResponse1.StatusCode = httpResponse.StatusCode;
restResponse1.StatusDescription = httpResponse.ReasonPhrase;
restResponse1.Request = request;
RestResponse restResponse2 = restResponse1;
foreach (var httpHeader in httpResponse.Headers)
restResponse2.Headers.Add(new Parameter()
{
Name = httpHeader.Key,
Value = (object)httpHeader.Value,
Type = ParameterType.HttpHeader
});
//foreach (var httpCookie in httpResponse.Content.)
// restResponse2.Cookies.Add(new RestResponseCookie()
// {
// Comment = httpCookie.Comment,
// CommentUri = httpCookie.CommentUri,
// Discard = httpCookie.Discard,
// Domain = httpCookie.Domain,
// Expired = httpCookie.Expired,
// Expires = httpCookie.Expires,
// HttpOnly = httpCookie.HttpOnly,
// Name = httpCookie.Name,
// Path = httpCookie.Path,
// Port = httpCookie.Port,
// Secure = httpCookie.Secure,
// TimeStamp = httpCookie.TimeStamp,
// Value = httpCookie.Value,
// Version = httpCookie.Version
// });
return restResponse2;
}
感谢您的任何想法
答案 0 :(得分：3)
_dataObserver为空，因为您没有订阅关联的observable。不要忘记可观察者是懒惰的......
您可以尝试以下方法：
ngOnInit() {
this.data = this._dataService.data$.subscribe(data => { // <-----
console.log(data);
});
this._dataService.getData();
}
修改
此外，您的代码中存在拼写错误：
this.data$ = new Observable(observer => this._todosObserver = observer).share();
您应该使用_dataObserver代替_todosObserver：
this.data$ = new Observable(observer => this._dataObserver = observer).share();