How to wait for a JSONModel.loadData() request in UI5

Question

In SAPUI5/OpenUI5, I have a JSONModel I populate by a file from server:

var oModel = new JSONModel();
oModel.loadData("http://127.0.0.1/data/config.json");
console.log(JSON.stringify(oModel.getData()));

The console logs undefined since the request is asynchronous.
How to make it synchronous so console.log() is called after the data was loaded?

Answer 1

Since UI5 version 1.64.0, the API loadData returns a Promise instance:

logLoadedData: async function () {
  const jsonModel = new JSONModel();
  await jsonModel.loadData("<host>/data/config.json");
  console.log(jsonModel.getData()); // after the loadData promise is resolved
},

Alternatively, there is also the API dataLoaded which returns a promise as well. It will resolve when all requests sent by loadData are finished. Here is a syntax without async-await:

doSomethingWith: async function (jsonModel) {
  // Not sure if the model has all data loaded? Just use dataLoaded:
  await jsonModel.dataLoaded();
  console.log(jsonModel.getData());
},

The API loadData is also called internally when the constructor function of JSONModel was called with a string (URL) as an argument. In that case, dataLoaded might come in handy as well.

Answer 2

Using synchronous ajax requests is not recommended as it blocks the UI and will probably result in a warning in the console.

You can attach to the Model.requestCompleted event to access the asynchronously loaded data:

oModel.attachRequestCompleted(function() {
        console.log(oModel.getData());
    });

Answer 3

The keyword you are looking for is "Deferred"-object --> it enables you to wait for an AJAX request in SAPUI5.

Check this for SAPUI5 context: SAPUI5 Wait for an Deferred-Object // wait for .done() function

Answer 4

You can use the attachRequestCompleted-listener from the Model ^[1]

model.attachRequestCompleted(function(){
    console.log(this.getData()); //"this" is the model
});

Another function to use is

$.get(url, function(response){
    console.log(response);
    model.setData(response);
});
// or
$.ajax(url, {
    success: function(){
        console.log(response);
        model.setData(response);
    }
});

This has the advantage that you can configure the request with every setting that jQuery.ajax accepts ^[2]