可选参数和子句。其中

我在用 angularcli 和 angularfire2 ,我的应用程序有一个方法,该方法带有可选参数,用于检索 firestore .

buildWomen(id: string, sex?: string, age?: string): Observable<Humans[]> {
    this.humanCollec = this.db.collection('human/' + id + '/women', ref => ref
      .where('sex', '==', sex) //--this can be null
      .where('age', '==', age); //--this can be null
    return this.humamObersArray = this.humanCollec.valueChanges();
  }

为了简化这个例子,我只显示了2个参数,但在实际方法中,我有10个参数。有一种最好的方法可以检查它或忽略它 .在哪里 当最后一个参数是 null

更新 以下内容:

…服务.ts

...
humanCol: AngularFirestoreCollection<Human>;
humanObersArray: Observable<Human[]>;
...
buildHuman(id: string, sex?: string, age?: string, ethnicity?: string, height?: string, weight?: string, religion?: string){ //: Observable<Human[]>
      //this.humanCol = 

      this.db.collection('human/'+id+'/women', ref => {
      let retVal = ref as any;
      if (sex != null) { retVal = retVal.where('sex', '==', sex) }
      if (age != null) { retVal = retVal.where('age', '==', age) }
      if (ethnicity != null) { retVal = retVal.where('ethnicity', '==', ethnicity) }
      if (height != null) { retVal = retVal.where('height', '==', height) }
      if (weight != null) { retVal = retVal.where('weight', '==', weight) }
      if (religion != null) { retVal = retVal.where('religion', '==', religion) }

      return retVal;
      //return this.humanObersArray = this.humanCol.valueChanges();
    });
  }