Javascript 包装ajax调用

我有一个代码，它将在select函数中生成一个ajax请求

  oSelect
    .select(function (oEvent) {
      return oEvent.getSource();
    })
    .select(function (oControl) {
      let oItem = oControl.getSelectedItem();
      let aKeys = oItem.getKey().split("/");
      return {plant: aKeys[0], wc: aKeys[1]};
    })
    .select(function (oSelectedItem) {

      let oModel = self.getModel("weightProtocolService");
      let oPlantFilter = new Filter("Plant", sap.ui.model.FilterOperator.EQ, oSelectedItem.plant);
      let oWcFilter = new Filter("WorkCenter", sap.ui.model.FilterOperator.EQ, oSelectedItem.wc);

      oModel.read("/CostCenterCalendarSet", {
        success: function (oData, oResponse) {
          return Rx.Observable.from(oResponse.data.results);

        },
        error: function (oError) {
          return Rx.Observable.throw(oError);
        },
        filters: [oPlantFilter, oWcFilter]
      });
    })
    .subscribe(function (oKey) {
      console.log(oKey);
    },
    function (err) {
      jQuery.sap.log.fatal(err);
    });

我这里的问题是，它将在ajax响应出现之前首先订阅

---

如何解决此问题？

如果

oModel.read

返回承诺，则您可以简单地执行以下操作：

....
return Observable.fromPromise(oModel.read("/CostCenterCalendarSet", {
        filters: [oPlantFilter, oWcFilter]
    })
);

---

---

如果

oModel.read

没有返回承诺，那么您需要一个自定义的可观察的：

....
return Observable.create(function(observer) {
    oModel.read("/CostCenterCalendarSet", {
        success: function (oData, oResponse) {
            return observer.onNext(oResponse.data.results);  // or just .next(..) in case you are using rxjs5+
        },
        error: function (oError) {
            return observer.onError(oError); // or just .error(..) in case you are using rxjs5+
        },
        filters: [oPlantFilter, oWcFilter]
    });
});

.mergeMap(function (oSelectedItem) {

  let oModel = self.getModel("weightProtocolService");
  let oPlantFilter = new Filter("Plant", sap.ui.model.FilterOperator.EQ, oSelectedItem.plant);
  let oWcFilter = new Filter("WorkCenter", sap.ui.model.FilterOperator.EQ, oSelectedItem.wc);

  return new Observable(observer => {
    oModel.read("/CostCenterCalendarSet", {
      success: function (oData, oResponse) {
        observer.next(oResponse.data.results);
      },
      error: function (oError) {
        observer.error(oError);
      },
      filters: [oPlantFilter, oWcFilter]
    });
  });
})

---

如果

oModel.read

返回一个承诺，那么您只需执行以下操作：

....
return Observable.fromPromise(oModel.read("/CostCenterCalendarSet", {
        filters: [oPlantFilter, oWcFilter]
    })
);

---

---

如果

oModel.read

没有返回承诺，那么您需要一个自定义的可观察的：

....
return Observable.create(function(observer) {
    oModel.read("/CostCenterCalendarSet", {
        success: function (oData, oResponse) {
            return observer.onNext(oResponse.data.results);  // or just .next(..) in case you are using rxjs5+
        },
        error: function (oError) {
            return observer.onError(oError); // or just .error(..) in case you are using rxjs5+
        },
        filters: [oPlantFilter, oWcFilter]
    });
});

.mergeMap(function (oSelectedItem) {

  let oModel = self.getModel("weightProtocolService");
  let oPlantFilter = new Filter("Plant", sap.ui.model.FilterOperator.EQ, oSelectedItem.plant);
  let oWcFilter = new Filter("WorkCenter", sap.ui.model.FilterOperator.EQ, oSelectedItem.wc);

  return new Observable(observer => {
    oModel.read("/CostCenterCalendarSet", {
      success: function (oData, oResponse) {
        observer.next(oResponse.data.results);
      },
      error: function (oError) {
        observer.error(oError);
      },
      filters: [oPlantFilter, oWcFilter]
    });
  });
})

---

假设RxJS 5，将最后一个select替换为mergeMap，并返回一个新的可观察对象：

....
return Observable.create(function(observer) {
    oModel.read("/CostCenterCalendarSet", {
        success: function (oData, oResponse) {
            return observer.onNext(oResponse.data.results);  // or just .next(..) in case you are using rxjs5+
        },
        error: function (oError) {
            return observer.onError(oError); // or just .error(..) in case you are using rxjs5+
        },
        filters: [oPlantFilter, oWcFilter]
    });
});

.mergeMap(function (oSelectedItem) {

  let oModel = self.getModel("weightProtocolService");
  let oPlantFilter = new Filter("Plant", sap.ui.model.FilterOperator.EQ, oSelectedItem.plant);
  let oWcFilter = new Filter("WorkCenter", sap.ui.model.FilterOperator.EQ, oSelectedItem.wc);

  return new Observable(observer => {
    oModel.read("/CostCenterCalendarSet", {
      success: function (oData, oResponse) {
        observer.next(oResponse.data.results);
      },
      error: function (oError) {
        observer.error(oError);
      },
      filters: [oPlantFilter, oWcFilter]
    });
  });
})

---

假设RxJS 5，将最后一个select替换为mergeMap，并返回一个新的可观察对象：

....
return Observable.create(function(observer) {
    oModel.read("/CostCenterCalendarSet", {
        success: function (oData, oResponse) {
            return observer.onNext(oResponse.data.results);  // or just .next(..) in case you are using rxjs5+
        },
        error: function (oError) {
            return observer.onError(oError); // or just .error(..) in case you are using rxjs5+
        },
        filters: [oPlantFilter, oWcFilter]
    });
});

.mergeMap(function (oSelectedItem) {

  let oModel = self.getModel("weightProtocolService");
  let oPlantFilter = new Filter("Plant", sap.ui.model.FilterOperator.EQ, oSelectedItem.plant);
  let oWcFilter = new Filter("WorkCenter", sap.ui.model.FilterOperator.EQ, oSelectedItem.wc);

  return new Observable(observer => {
    oModel.read("/CostCenterCalendarSet", {
      success: function (oData, oResponse) {
        observer.next(oResponse.data.results);
      },
      error: function (oError) {
        observer.error(oError);
      },
      filters: [oPlantFilter, oWcFilter]
    });
  });
})