If JSON model defined in manifest, how to know model data is loaded when needed in controller?

[mii_guy]

I have JSONModel defined in manifest. When arrive in oninit of Page1 of app, my model is sometimes not loaded.

Line below sometimes errors as model is not loaded:

var oServlet = this.getOwnerComponent().getModel().getProperty("/Rowsets/Rowset/0/Row");

Is attachRequestCompleted needed in controller code, or is there a newer/better way to do this in SAPUI5?

Would a promise be better?

If so, can I use promise with JSONModel?

If so, how?

I have noticed a UI5 function in some online examples: oModel.metadataLoaded(true).then(...

Is "metadataLoaded" function only for OData models?

If so, is there a related JSON function other than attachRequestCompleted?

If attachRequestCompleted is needed, must I recreate the model. Example:

var oModel = new JSONModel(); // >>> This seems inefficient as model is already defined in manifest?

oModel.attachRequestCompleted(){function(){

console.log("manifest model is loaded.")

}

Manifest entries

Is "type" required in mainService?

"dataSources": {

"mainService": {

"uri": "/XMII/PropertyAccessServlet?Mode=List&content-type=text/json",

"type": "JSON"

}

},

Is "type" required in ""?

"models": {

"": {

"dataSource": "mainService",

"type": "sap.ui.model.json.JSONModel",

"preload": true

}

},

I am new to UI5 and would like to learn!

Thanks very much for any information that can be provided.

[sveabecker]

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[boghyon · Accepted solution]

Since UI5 1.64, JSONModel provides the API dataLoaded() that returns a promise (which is similar to the `metadataLoaded(true)` in v2.ODataModel). Take a look at https://stackoverflow.com/a/63892279/5846045.

doSomethingWith: async function (myJSONModel) {
  await myJSONModel.dataLoaded(); // since UI5 v1.64
  const data = myJSONModel.getProperty("/...");
},

[mii_guy · Accepted solution]

This code has allowed me to create a solution that is working! Thank you very much for the example and the links!