switchMap类型void不能分配给类型observateInput<{}>

Argument of type '(result: any) => void' is not assignable to parameter of type '(value: any, index: number)' => ObservableInput<{}>

在我的切换地图上使用。

--不带switchMap的简单示例----

购物车组件

ngOnInit() {
    this.systemPreferences.getPreferences()
        .subscribe(
            (result: any) => {
                this.headerTitle = result.title || '';
            },
            (err) => {
                console.log('there has been an error');
            },
            () => // Some completion code
        );
}

系统首选项.service.ts:

const CACHE_SIZE = 1;

export class SystemPreferences {
    private $cache: Observable<Object>

    private requestConfig() {
         return this.http.get("/api/some/endpoint").pipe(
             map(response => response.value)
         );
    }

    public getPreferences() {
        if (!this.cache$) {
            this.cache$ = this.requestConfig().pipe(
             shareReplay(CACHE_SIZE)
            );
        }

        return this.cache$;
    }
}

/api/some/endpoint示例响应:

{
    "appName": "Tables Forks and Spoons",
    "title": "My title",
    "regionUrls": [
        "http://www.region1.com:8021",
        "http://www.region2.com:8021",
        "http://www.region3.com:8021",
        "http://www.region4.com:8021"
    ],
    "nonRegionUrls": [
        "http://www.non-region1.com:8021",
        "http://www.non-region2.com:8021",
        "http://www.non-region3.com:8021",
        "http://www.non-region4.com:8021"
    ]
}

--switchMap的类型错误简单示例----

购物车组件

ngOnInit() {
    this.systemPreferences.getPreferences()
        .pipe(
            .switchMap((result: any) => {

               this.systemPreferences.getLiveUrl(result['regionUrls']);

            }))
        .subscribe(
            (result: any) => {
                this.liveLink = result.liveLink; // result.livelink is added as part of this.systemPreferences.getLiveUrl above
                this.headerTitle = result.title || '';
            },
            (err) => {
                console.log('there has been an error');
            }
        );
}

const CACHE_SIZE = 1;

export class SystemPreferences {
    private $cache: Observable<Object>

    private requestConfig() {
         return this.http.get("/api/some/endpoint").pipe(
             map(response => response.value)
         );
    }

    public getPreferences() {
        if (!this.cache$) {
            this.cache$ = this.requestConfig().pipe(
             shareReplay(CACHE_SIZE)
            );
        }

        return this.cache$;
    }

    public getLiveUrl(urls: any) {
        let promises = [];

        urls.forEach((url) => {
           promises.push(this.http.get(url + 'some/endpoint/')); 
        });

        const results = forkJoin(promises) {
            .subscribe((data: any) => {
                return this.getBest(data);
            }
        }
    }

    public getBest(data: any) {
        // Loops through data, and returns a single URL as a string
        // 'http//www.thebesturltouse.com'
    }
}

尝试返回建议的第二个可观测值(见下文)具有与上文相同的类型void error。

购物车组件

ngOnInit() {
    this.systemPreferences.getPreferences()
        .pipe(
            .switchMap((result: any) => {
               return this.systemPreferences.getLiveUrl(result['regionUrls']);
            }))
        .subscribe(
            (result: any) => {
                this.liveLink = result.liveLink; // result.livelink is added as part of this.systemPreferences.getLiveUrl above
                this.headerTitle = result.title || '';
            },
            (err) => {
                console.log('there has been an error');
            }
        );
}

系统首选项.service.ts:

const CACHE_SIZE = 1;

export class SystemPreferences {
    private $cache: Observable<Object>
    private $switchObs: Observable<Object> 

    private requestConfig() {
         return this.http.get("/api/some/endpoint").pipe(
             map(response => response.value)
         );
    }

    public getPreferences() {
        if (!this.cache$) {
            this.cache$ = this.requestConfig().pipe(
             shareReplay(CACHE_SIZE)
            );
        }

        return this.cache$;
    }

    public getLiveUrl(urls: any) {
        let promises = [];

        urls.forEach((url) => {
           promises.push(this.http.get(url + 'some/endpoint/')); 
        });

        const results = forkJoin(promises) {
            .subscribe((data: any) => {
                this.$switchObs = this.getBest(data);
                return this.$switchObs;
            }
        }
    }

    public getBest(data: any) {
        // Loops through data, and returns a single URL as a string
        // 'http//www.thebesturltouse.com'
    }
}

更新到多个switchMaps

ngOnInit() {
    this.systemPreferences.getPreferences()
        .pipe(
            .switchMap((result: any) => {
               return this.systemPreferences.getLiveUrl(result['regionUrls']);
            }),
            .switchMap((liveRegion: any) => {
               return this.systemPreferences.getBest(liveRegion);
            }))
        .subscribe(
            (bestUrl: String) => {
                console.log('best');
                console.log(bestUrl);
            },
            (err) => {
                console.log('there has been an error');
            }
        );
}

系统首选项.service.ts:

const CACHE_SIZE = 1;

export class SystemPreferences {
    private $cache: Observable<Object>
    private $switchObs: Observable<String> 

    private requestConfig() {
         return this.http.get("/api/some/endpoint").pipe(
             map(response => response.value)
         );
    }

    public getPreferences() {
        if (!this.cache$) {
            this.cache$ = this.requestConfig().pipe(
             shareReplay(CACHE_SIZE)
            );
        }

        return this.cache$;
    }

    public getLiveUrl(urls: any) {
        let promises = [];

        urls.forEach((url) => {
           promises.push(this.http.get(url + 'some/endpoint/')); 
        });

        return forkJoin(promises);
    }

    public getBest(data: any) {
        // Loops through data, and returns a single URL as a string
        // 
        return this.$switchObs; // = 'http//www.thebesturltouse.com'
    }
}

'best'
h
'best'
t
'best'
t
'best'
p
'best'
:
'best'
/
'best'
/
'best'
w
'best'
w
'best'
w
'best'
.
'best'
b
etc etc etc

更新。

这不是解决这个问题的最好办法。