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maintained data that is held in memory.

When constructed, it has a property called "data" that holds the initial data of the store.

dojo/store/Observable

When one executes a query on a store and that store is an Observable, then a function called

"observe()" may be executed on the returned results. This causes the results to be "monitored"

and if the results would change as if executed again, the function passed by "observe()" is

called. This function is passed three parameters:

• item – The item that changed

• removedFrom – Where the item was removed from

• insertedInto – Where the item was inserted into

The formal syntax of observe() is:

observe(function(item, removedFrom, insertedInto), includeObjectUpdates)

The includeObjectUpdates defines whether or not the changes to the content of the data will

be flagged. The default is false.

Deferred and asynchronous processing – dojo/Deferred

Within Dojo, there are times where we wish some action to be executed and, when completed, to

invoke a callback with the results. This is very common with AJAX programming. Dojo provides

assistance with this function through the "Deferred" capabilities.

Here is a high level skeleton

function myAsync() {

var deferred = new Deferred();

doSomethingInBackground(function(X) {

deferred.resolve(X);

});

return deferred.promise;

}

// caller

myAsync().then(function(Y) {

… process result;

});

The concept is that when something may happen in the background, the provider of that something

returns an instance of a "Deferred". Deferred has a method on it called "then()" which takes

a function as a parameter. When the background thing has completed, the provider of the

background service calls the method called "resolve()" on the Deferred object. This is what

triggers the "then()" function.

If the asynchronous function should fail, it may issue the "reject()" method to indicate that this has

happened.

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Servis-Rhino 4211B Betriebsanweisung Seite 201