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jQuery checkbox checked state changed event

I want an event to fire client side when a checkbox is checked / unchecked:

$('.checkbox').click (function(){
  var thisCheck = $(this);

  if ( thischeck.is(':checked') ) {
    // Do stuff
  }
});

Basically I want it to happen for every checkbox on the page. Is this method of firing on the click and checking the state ok?

I'm thinking there must be a cleaner jQuery way. Anyone know a solution?

jQuery - Detect value change on hidden input field

I have a hidden text field whose value gets updated via an AJAX response.

<input type="hidden" value="" name="userid" id="useid" />

When this value changes, I would like to fire an AJAX request. Can anyone advise on how to detect the change?

I have the following code, but do not know how to look for the value:

$('#userid').change( function() {  
    alert('Change!'); 
}) 

Understanding events and event handlers in C#

I understand the purpose of events, especially within the context of creating user interfaces. I think this is the prototype for creating an event:

public void EventName(object sender, EventArgs e);

What do event handlers do, why are they needed, and how do I to create one?

jQuery checkbox change and click event

I have

<input type="checkbox" id="checkbox1" /> <br />
<input type="text" id="textbox1" />

and

$(document).ready(function() {
    //set initial state.
    $('#textbox1').val($(this).is(':checked'));

    $('#checkbox1').change(function() {
        $('#textbox1').val($(this).is(':checked'));
    });

    $('#checkbox1').click(function() {
        if (!$(this).is(':checked')) {
            return confirm("Are you sure?");
        }
    });
});

JSFIDDLE link

Here the changed event updates the textbox value with the checkbox status. I use the click event to confirm the action on uncheck. If the user selects cancel, the check mark is restored but the change even fires before confirmation leaving things in a inconsistent state (the textbox says false when the checkbox is checked). How can I deal with the cancellation and keep textbox value consistent with the check state?

Thanks

UITextField text change event

How can I detect any text changes in a textField? The delegate method shouldChangeCharactersInRange works for something, but it did not fulfill my need exactly. Since until it returns YES, the textField texts are not available to other observer methods.

e.g. in my code calculateAndUpdateTextFields did not get the updated text, the user has typed.

Is their any way to get something like textChanged Java event handler.

- (BOOL)textField:(UITextField *)textField 
            shouldChangeCharactersInRange:(NSRange)range 
            replacementString:(NSString *)string 
{
    if (textField.tag == kTextFieldTagSubtotal 
        || textField.tag == kTextFieldTagSubtotalDecimal
        || textField.tag == kTextFieldTagShipping
        || textField.tag == kTextFieldTagShippingDecimal) 
    {
        [self calculateAndUpdateTextFields];

    }

    return YES;
}

C# pattern to prevent an event handler hooked twice [duplicate]

Duplicate of: How to ensure an event is only subscribed to once and Has an event handler already been added?

I have a singleton that provides some service and my classes hook into some events on it, sometimes a class is hooking twice to the event and then gets called twice. I'm looking for a classical way to prevent this from happening. somehow I need to check if I've already hooked to this event...

Event system in Python

What event system for Python do you use? I'm already aware of pydispatcher, but I was wondering what else can be found, or is commonly used?

I'm not interested in event managers that are part of large frameworks, I'd rather use a small bare-bones solution that I can easily extend.

How to debug JavaScript/jQuery event bindings with Firebug (or similar tool)

I need to debug a web application that uses jQuery to do some fairly complex and messy DOM manipulation. At one point, some of the events that were bound to particular elements, are not fired and simply stop working.

If I had a capability to edit the application source, I would drill down and add a bunch of Firebug console.log() statements and comment/uncomment pieces of code to try to pinpoint the problem. But let's assume I cannot edit the application code and need to work entirely in Firefox using Firebug or similar tools.

Firebug is very good at letting me navigate and manipulate the DOM. So far, though, I have not been able to figure out how to do event debugging with Firebug. Specifically, I just want to see a list of event handlers bound to a particular element at a given time (using Firebug JavaScript breakpoints to trace the changes). But either Firebug does not have the capability to see bound events, or I'm too dumb to find it. :-)

Any recommendations or ideas? Ideally, I would just like to see and edit events bound to elements, similarly to how I can edit DOM today.

event.preventDefault() vs. return false

When I want to prevent other event handlers from executing after a certain event is fired, I can use one of two techniques. I'll use jQuery in the examples, but this applies to plain-JS as well:

1. event.preventDefault()

$('a').click(function (e) {
    // custom handling here
    e.preventDefault();
});

2. return false

$('a').click(function () {
    // custom handling here
    return false;
});

Is there any significant difference between those two methods of stopping event propagation?

For me, return false; is simpler, shorter and probably less error prone than executing a method. With the method, you have to remember about correct casing, parenthesis, etc.

Also, I have to define the first parameter in callback to be able to call the method. Perhaps, there are some reasons why I should avoid doing it like this and use preventDefault instead? What's the better way?

Event when element added to page

This was previously discussed here: How to do an action when an element is added to a page using Jquery?

The responder suggested triggering a custom event whenever a div was added to the page. However, I'm writing a Chrome extension and don't have access to the page source. What are my options here? I guess in theory I could just use setTimeout to continually search for the element's presence and add my action if the element is there.

.NET Events - What are object sender & EventArgs e?

What do sender and eventArgs mean/refer to? How can I make use of them (for the scenario below)?

Scenario:

I'm trying to build a custom control with a delete function, and I want to be able to delete the control that was clicked on a page that contains many of the same custom control.

How can I catch a ctrl-c event? (C++)

How do I catch a ctrl-c event in C++?

jQuery: $().click(fn) vs. $().bind('click',fn);

When using jQuery to hookup an event handler, is there any difference between using the click method

$().click(fn)

versus using the bind method

$().bind('click',fn);

Other than bind's optional data parameter.

Do event handlers stop garbage collection from occuring?

If I have the following code:

MyClass pClass = new MyClass();
pClass.MyEvent += MyFunction;
pClass = null;

Will pClass be garbage collected? Or will it hang around still firing its events whenever they occur? Will I need to do the following in order to allow garbage collection?

MyClass pClass = new MyClass();
pClass.MyEvent += MyFunction;
pClass.MyEvent -= MyFunction;
pClass = null;

Changing UIButton text

So I'm trying to update the text on a UIButton when I click it. I'm using the following line to change the text:

calibrationButton.titleLabel.text = @"Calibration";

I have verified that the text is changing, but when I run the app and I click on the button, it changes to "Calibration" for a split second and then goes right back to its default value. Any ideas why this might be happening? Is there some sort of refresh function I need to be calling?