Angular TypeError:无法读取属性'；下一个'；指未定义的行为主体

我的代码在运行时和执行console.logs时都正常工作。日志显示，

isqrcodeshow$

未定义

我收到错误

TypeError:无法读取未定义的属性“next”

TypeError: Cannot read property 'next' of undefined
    at <Jasmine>
    at SafeSubscriber.setQrShown [as _next] (http://localhost:9876/_karma_webpack_/src/app/modules/review-sign/services/qr-code/qr-code.service.ts:24:25)
    at SafeSubscriber.__tryOrUnsub (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Subscriber.js:183:1)
    at SafeSubscriber.next (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Subscriber.js:122:1)
    at Subscriber._next (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Subscriber.js:72:1)
    at Subscriber.next (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Subscriber.js:49:1)
    at MapSubscriber._next (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/operators/map.js:35:1)
    at MapSubscriber.next (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Subscriber.js:49:1)
    at Observable._subscribe (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/util/subscribeToArray.js:3:1)
    at Observable._trySubscribe (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Observable.js:42:1)
    at Observable.subscribe (http://localhost:9876/_karma_webpack_/node_modules/rxjs/_esm2015/internal/Observable.js:28:1)

这是我使用BehaviorSubject

服务添加两个测试的时候。isqrcodeShowed$

• 当给定国家/地区不在列表中时，IsqrCodeShowed$应为false
• 当给定国家/地区在列表中时，IsqrCodeShowed$应为真

---

我还使用ff命令

ng test测试它——include file path/file.spec.ts

setqrshow

不是一个箭头函数，这里

//...
    .subscribe(this.setQrShown);

此

上下文丢失。您可以更详细一些：

    .subscribe(value => this.setQrShown(value));

或将

setqr设置为箭头函数：

setQrShown = (country: string): void => {

我的错误，看起来像是一个
词法范围界定问题。谢谢你的回答：）
    .subscribe(value => this.setQrShown(value));

setQrShown = (country: string): void => {