Javascript 在Angular/Firestore中设置服务变量

我无法将变量传递到角度数据处理服务

我的应用程序运行查询以获取幻灯片的编号

服务

getAudience() 
{
    return this.firestore.collection('sessions').doc('operaHouse').collection('questions', ref=>ref.where("isApproved", "==", true).orderBy("queueOrderNumber", "asc").limit(1))
}

getAnswerFromNum(sliden: number) { 
    return this.firestore.collection('sessions').doc('operaHouse').collection('answerSlides', ref=> ref.where("slideNumber", "==", sliden))
}

组成部分

getSlideNum = () => this.qandaService.getAudience().snapshotChanges().subscribe(res =>(this.slideNum = res[0].payload.doc.data().answerNum)) 

getAssignedAnswer = () => this.qandaService.getAnswerFromNum(this.slideNum).snapshotChanges().subscribe(res =>(this.assignedAnswer = res))

这会将

this.slidenum

返回到组件

然后，当我将

this.slidenum

发送到下一个查找查询时，变量没有传递，查询失败

服务

getAudience() 
{
    return this.firestore.collection('sessions').doc('operaHouse').collection('questions', ref=>ref.where("isApproved", "==", true).orderBy("queueOrderNumber", "asc").limit(1))
}

getAnswerFromNum(sliden: number) { 
    return this.firestore.collection('sessions').doc('operaHouse').collection('answerSlides', ref=> ref.where("slideNumber", "==", sliden))
}

组成部分

getSlideNum = () => this.qandaService.getAudience().snapshotChanges().subscribe(res =>(this.slideNum = res[0].payload.doc.data().answerNum)) 

getAssignedAnswer = () => this.qandaService.getAnswerFromNum(this.slideNum).snapshotChanges().subscribe(res =>(this.assignedAnswer = res))

我相信这是一个操作顺序问题，但我不确定如何解决。任何帮助都将不胜感激

谢谢

---

A.

您能否提供查询失败时出现的错误？