KnockoutJS:淡出其他东西后淡出

Question

假设我有一组3个单选按钮:

<div>
    <label>
        <input type="radio" name="Who" value="Myself" 
            checked="@isMyselfChecked" data-bind="checked: who" />
        Mine
    </label>
    <label>
        <input type="radio" name="Who" value="MemberId" 
            checked="@isMemberIdChecked" data-bind="checked: who" />
        I know the member's ID
    </label>
    <label>
        <input type="radio" name="Who" value="MemberUrl" 
            checked="@isMemberUrlChecked" data-bind="checked: who" />
        I know the member's URL
    </label>
</div>

当用户选择第一个单选按钮(Mine/Myself)时,不需要额外的输入.但是,在选择第二或第三时,额外的输入是必需的:

<div>
    <input type="text" name="MemberId" placeholder="Enter Member ID" 
        data-bind="toggleWho: who()" style="display: none" />
    <input type="text" name="MemberUrl" placeholder="Enter Member URL" 
        data-bind="toggleWho: who()" style="display: none; width: 450px;" />
</div>

只需拥有data-bind="visible: who() === '[MemberId|MemberUrl]'"依赖文本框就足够了.但是,如果我想添加淡入/淡出过渡怎么办？

我尝试了fadeVisible bindingHandler淘汰网站的示例自定义,我理解它是如何工作的.然而,这将同时在文本框中淡出和淡出.如果'MemberId'选择了'MemberUrl'无线电,并且用户选择了无线电,我希望MemberId文本框在文本框淡入之前MemberUrl淡出.

以下是我现在所拥有的,它有效,但我不认为这是最佳的.在前一个元素消失之前,怎么还能告诉他们不执行淡入淡出？我需要另一个ko.observale,还是可能ko.computed？

var viewModel = {
    fadeSpeed: 150,
    who: ko.observable($('input[type=radio][name=Who]:checked').val())
};

ko.bindingHandlers.toggleWho = {
    init: function (element, valueAccessor) {
        var value = valueAccessor();
        var unwrapped = ko.utils.unwrapObservable(value);
        if (unwrapped === element.name)
            $(element).show();
    },
    update: function (element, valueAccessor) {
        var value = valueAccessor();
        var unwrapped = ko.utils.unwrapObservable(value);

        // when selected value is myself, fade out the visible one, if any
        if (unwrapped === 'Myself') {
            $('input[type=text][name=MemberId]:visible')
                .fadeOut(viewModel.fadeSpeed);
            $('input[type=text][name=MemberUrl]:visible')
                .fadeOut(viewModel.fadeSpeed);
        }

            // when selected value is memberid, may need to fade out url first
        else if (unwrapped === 'MemberId') {
            if ($('input[type=text][name=MemberUrl]:visible').length > 0) {
                $('input[type=text][name=MemberUrl]:visible')
                    .fadeOut(viewModel.fadeSpeed, function () {
                        $('input[type=text][name=MemberId]')
                            .fadeIn(viewModel.fadeSpeed);
                    });
            } else {
                $('input[type=text][name=MemberId]')
                    .fadeIn(viewModel.fadeSpeed);
            }
        }

            // when selected value is memberurl, may need to fade out id first
        else if (unwrapped === 'MemberUrl') {
            if ($('input[type=text][name=MemberId]:visible').length > 0) {
                $('input[type=text][name=MemberId]:visible')
                    .fadeOut(viewModel.fadeSpeed, function () {
                        $('input[type=text][name=MemberUrl]')
                            .fadeIn(viewModel.fadeSpeed);
                });
            } else {
                $('input[type=text][name=MemberUrl]')
                    .fadeIn(viewModel.fadeSpeed);
            }
        }
    }
};

ko.applyBindings(viewModel);

Answer 1

你将不得不适应这一点以适应你的例子,但我需要简化它来测试这个小提琴.

这是绑定:

var previousElement = null;
ko.bindingHandlers.fadeSwitcher = {
    init: function(element, valueAccessor) {
        var value = valueAccessor();
        $(element).toggle(ko.utils.unwrapObservable(value));
    },
    update: function(element, valueAccessor) {

        var value = ko.utils.unwrapObservable(valueAccessor());
        if (value) {
            if (previousElement == null) { // initial fade
                $(element).fadeIn();
            } else {
                $(previousElement).fadeOut('fast', function() {
                    $(element).fadeIn();
                });
            }
            previousElement = element;
        }        
    }
};