There is a necessary pause needed between carrying out two statements

I am currently working with extjs 4.2 and I have encountered a situation where I am loading the store object in the following manner:

var userDetailStore = Ext.create('Ext.data.Store', {
    model: 'Person.DetailsModel',
    autoLoad: true,
    
    proxy: {
        type: 'ajax',
        method: 'POST',
        url: 'getValueAction.action',
        reader: {
            type: 'json',
            root: 'details'
        },
        writer: {
            type: 'json',
            root: 'details'
        }
    },
    fields: ['id', 'loginName', 'referenceId', 'name']
}); // Here I load the store which will definitely contain a list of values.

Following the store creation, I attempt to retrieve the referenceId of the first value from the store object using this code:

var empId = userDetailStore.getAt(0).get('referenceId');

However, I encounter an error because at that point, the getCount() function of the userDetailStore object is returning zero. Interestingly, if I include an alert('loading data'); statement before retrieving the referenceId, the code works as expected. The line userDetailStore.getCount() returns the correct count.

It seems like there may be a timing issue between loading the store and accessing it, but I would prefer not to rely on alert statements for this. I have tried using the sleep() method instead of alert, but that did not resolve the issue either (and I don't want to freeze the browser with sleep()).

Am I missing something in how I'm loading the store? Is there a standard way to ensure my code runs after the store has completely loaded?

If anyone could provide some guidance, I would greatly appreciate it.

Regards, Dev

Answer №1

Vijay has provided the correct answer, but I wanted to elaborate on the concept to help clarify how it aligns with your current task.

It is crucial to understand that when making an AJAX request, the process is asynchronous. This means that once you initiate an asynchronous request, your script will not wait for it to complete before moving on to the next line of code.

This explains why you were not seeing a "count" in your store. While the async request was fetching data from the server and processing it, the rest of your code continued executing without waiting for the response (highlighting the power of async requests).

Adding an alert seemed to temporarily resolve the issue because it paused the script until you interacted with it. During this pause, the async request could finish its operation and update the original object.

While implementing a delay might seem like a solution, it can be unreliable due to various factors affecting the duration of async requests. This unpredictability highlights the importance of utilizing events like load() in handling async operations effectively.

Familiarizing yourself with callbacks and event handling may require a shift from a linear mindset, but it is essential when working with AJAX requests and frameworks like ExtJS 4 to ensure consistency and efficiency in application development.

Answer №2

Employ the on load event to retrieve the count only after complete loading

userDetailStore.on('load', function(){
                alert("Fully loaded");
            });

Answer №3

For optimal performance, disable autoload and trigger the load manually using the load() function when needed.

store.load({
    callback: function(records, operation, success) {
        // Implement logic to handle data after loading
    },
    scope: this
});

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