sap.ui.model.Binding attachChange is always fired regardless of the sPath and context of binding

[sap]

sap.ui.model.Binding attachChange is always fired regardless of the sPath and context of binding

[goligo]

Hi Trevor,

looks like you didn't look at any documentation or samples regarding databinding, but just try to put together some classes according to the JSDOC. Please do not create instances of context or bindings directly, but use the model API for that purpose, which will return bindings of the correct type which work as expected:

http://jsbin.com/gaca/62/edit

As you might have noticed there are different model implementations, but they share a common interface so that controls do not need to take care of differences in the model implementations. This common interface is defined in the abstract model base classes (in sap.ui.model).

Regards,
Malte

[goligo]

The class sap.ui.model.Binding is an abstract base class and should not be used directly. It contains the default implementation of change handling which fires a change event on any model change. Subclasses like sap.ui.model.json.JSONPropertyBinding do only fire, if their bound property value was modified.

[matz3]

As @goligo said, using the actual implementation (JSONPropertyBinding in this case) will work as expected. Therefore I am closing this issue.

[trevornc]

Thank you for the update, and I will certainly use the sap.ui.model.json.JSONPropertyBinding. Can we re-open this bug on the documentation as from what I can see there is no reference to this class anywhere in the documentation, neither in the API or in the Developer Guide.

JSONTreeBinding
JSONListBinding
JSONPropertyBinding

Unless, I am looking in the wrong place for the information https://openui5.hana.ondemand.com/#search.html?q=jsonPropertyBinding.

Regards,
Trevor

[akudev]

Hmm, right... we are clarifying now whether they are intentionally missing or what's going on there. Hold on...

[akudev]

Ok, so the concrete "JSON*" classes are intentionally not documented because they should not be used directly. Instead, "PropertyBinding" etc. are documented and they are the common base classes that hide the model type specific details behind the common API.

Another running example which also uses actual controls and gets the bindings from the controls is here:
http://jsbin.com/gaca/63/edit

Regards
Andreas

[trevornc]

Andreas, Malte,

Thank you both for the clarifications. I am not sure why I didn't grasp the binding examples I guess I was trying to understand the process purely using the API documentation.

Please feel free to make this closed.

Regards,
Trevor

[trevornc]

Andreas, Malte,

Is it possible to attach a change listener to part of a model ( in particular a JSONModel ) for example:

   var oData = {
        myObj1 : {
            item : "Item1"
        },
        myObj2 : {
            item : "Item2",
            item2 : {
                subItem : {
                    leafItem : "Aleaf"
                }
            }
        },
        myObj3 : {
            item : "Item3",
            thing : "Thing3"
        }
    };

Is it possible to "attachChange" to /myObj2/item2 so that any changes under this node (such as "leafItem") would fire the event ?

Regards,
Trevor

[trevornc]

Looking at the code more closely, it would appear that using bindProperty to bind to a property that is an object does not work. The problem is in the code show below. When this._getValue() refers to an object, it returns the reference to the object (in the model), this means that later when the value is compared to the model it is always the same.

var ClientPropertyBinding = PropertyBinding.extend("sap.ui.model.ClientPropertyBinding", /** @lends sap.ui.model.ClientPropertyBinding */ {

    constructor : function(oModel, sPath, oContext, mParameters){
        PropertyBinding.apply(this, arguments);
        this.oValue = this._getValue();
    }

A solution would be to detect that the returned value is an object and then clone it using the jQuery.extend functionality.

[warstick]

@goligo HI Goligo..

i am trying to track the changes in JSONModel. But i couldn't able to track the data changes.

Here is my jsonmodel data.

{
"sample1": [ {"property1": "1"}, {"property2": "1"} ],
"sample2": [ {"property1": "1"}, {"property2": "1"} ]

}

Here, i want to track the "sample1" changes. is there any way of tracking these changes ?

[StErMi]

Is there a live example that correctly use sap.ui.model.json.JSONPropertyBinding?

[fredericDaigle]

Hi @trevornc , did you ever find a way to fire the event only when a specified node of the model is changed instead of when any part is changed?

[subhashchaganti]

Thanks , whole thread helped alot!!!

[johnmiroki]

Thinking out of the box, maybe we should ditch the event based reactivity altogether and jump on the modern observability/reactivity wagon by leveraging Proxy. I am in awe when I learn about what Vue can do with method/watch/computed and intend to introduce them to UI5 ego system.