How can I call the attach / detach events with a named function?

I have a function which needs to attach and detach a handler to the event “requestCompleted” of the OData model to get the URL from the header in order to download the data as an Excel file.

onClickAction: function (oEvent) {
    var model = this.getView().getModel();
    model.attachRequestCompleted(this.downloadODataAsExcel);
    var btnGo = this.getView().byId("btn");
    btnGo.firePress();
    model.detachRequestCompleted(this.downloadODataAsExcel, this);
},

downloadODataAsExcel: function (evt) {
    var url;
    url = evt.getParameters() && evt.getParameters().url;
    url = "/sap/opu/odata/sap/ZService/" + url + "&$format=xlsx";
    sap.m.URLHelper.redirect(url, true);
},

I am trying to detach the event afterwards to prevent snowballing of the event which causes the file to download n+1 times each time you click the download button.

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Update: this is the code I ended up with

onClickAction: function (oEvent) {
    var model = this.getView().getModel();
    model.attachRequestCompleted(this.downloadOdataAsExcel, this);
    var btnGo = this.getView().byId("btn");
    btnGo.firePress();
},

downloadODataAsExcel: function (evt) {
    var url;
    url = evt.getParameters() && evt.getParameters().url;
    url = "/sap/opu/odata/sap/Z_SERVICE/" + url + "&$format=xlsx";
    sap.m.URLHelper.redirect(url, true);
    var model = this.getView().getModel();
    model.detachRequestCompleted(this.downloadODataAsExcel, this);
}

The detach needs to be within the function otherwise the listener will be detached before the requestCompleted event fires.

Answer

Try this:

model.attachRequestCompleted(this.downloadOdataAsExcel, this);

And then try to access the ‘evt’ object.