Question

在我的angular2应用中，我有服务向网址发送获取请求。

这是我的服务：

    import {Http} from '@angular/http';
    import {Observable} from 'rxjs/Observable';
    import 'rxjs/add/operator/map';
    import {Injectable} from '@angular/core';
    import {Gallery} from './gallery';

    @Injectable()
    export class InstagramService{

        constructor(private _http:Http){

        }

        getGallery(username: string) : Observable<Gallery> {
            var result=this._http.get("https://www.instagram.com/"+username+"/media/").map(res => res.json());
 console.log(result);
        return result;
        }

    }

我已将返回类型定义为Observable<Gallery>，但它抱怨：

A function whose declared type is neither 'void' nor 'any' must return a value

这段代码出了什么问题？

Answer 1

如果您声明了返回类型，那么为什么不返回任何内容？

在这种情况下，通常这就是你想要的。

R version 3.2.2 (2015-08-14)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows Server 2012 x64 (build 9200)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] doParallel_1.0.10   iterators_1.0.8     earth_4.4.4         plotmo_3.1.4        TeachingDemos_2.10 
 [6] plotrix_3.6-2       glmnet_2.0-5        foreach_1.4.3       Matrix_1.2-4        caretEnsemble_2.0.0
[11] caret_6.0-64        ggplot2_2.1.0       RevoUtilsMath_8.0.1 RevoUtils_8.0.1     RevoMods_8.0.1     
[16] RevoScaleR_8.0.1    lattice_0.20-33     rpart_4.1-10       

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.4        compiler_3.2.2     nloptr_1.0.4       plyr_1.8.3         tools_3.2.2       
 [6] lme4_1.1-11        digest_0.6.9       nlme_3.1-126       gtable_0.2.0       mgcv_1.8-12       
[11] SparseM_1.7        gridExtra_2.2.1    stringr_1.0.0      MatrixModels_0.4-1 stats4_3.2.2      
[16] grid_3.2.2         nnet_7.3-12        data.table_1.9.6   pbapply_1.2-1      minqa_1.2.4       
[21] reshape2_1.4.1     car_2.1-2          magrittr_1.5       scales_0.4.0       codetools_0.2-14  
[26] MASS_7.3-45        splines_3.2.2      pbkrtest_0.4-6     colorspace_1.2-6   quantreg_5.21     
[31] stringi_1.0-1      munsell_0.4.3      chron_2.3-47

getGallery(username: string) : Observable<Gallery> { return this._http.get("https://www.instagram.com/"+username+"/media/").map(res => res.json()); }可能并不是您所期望的，因为var result会返回_http.get(...)而非值。

然后Observable的来电者可以订阅，以便在值到达时收到通知。

getGallery()

当值到达时，系统会调用instagramService.getGallery.subscribe((result) => this.galleryData = result);并将(result) => this.galleryData = result分配给您当前组件或服务的result。

声明类型既不是＆＃39; void＆＃39;也没有任何＆＃39;必须返回一个值

1 个答案: