Angular 5 HTTP.get返回無法讀取未定義的長度

Question

正在通過我的服務進行此調用，以檢索URL以下載文檔：

return this.http.get(this.buildUrl('issueDocument', 'get', pathParams), { responseType: 'blob', params: queryParams });

我已經測試過this.http.get中的buildURL正常工作，但是this.http.get的返回引發此錯誤

ERROR TypeError: Cannot read property 'length' of undefined
at HttpHeaders.applyUpdate (http.js:322)
    at eval (http.js:269)
    at Array.forEach (<anonymous>)
    at HttpHeaders.init (http.js:269)
    at HttpHeaders.forEach (http.js:368)
    at Observable.eval [as _subscribe] (http.js:2172)
    at Observable._trySubscribe (Observable.js:172)
    at Observable.subscribe (Observable.js:160)
    at CatchOperator.call (catchError.js:80)
    at Observable.subscribe (Observable.js:157)

有什么想法嗎？ 我無法理解為什么會發生這種情況...在“開發工具”網絡標簽中，它甚至沒有顯示網絡通話...

Answer 1

從錯誤消息看來，您只需要不讓undefined傳遞到標題的.set(...)中即可。

我這樣做：

 getHeaders() {
    const headers = new HttpHeaders();
    headers
      .set('Content-Type', 'application/json')
      .set('Authorization', localStorage.getItem('token') || '');
    return headers;
  }