值更改时调用自定义方法

发布于 2024-12-16 10:31:22 字数 618 浏览 0 评论 0原文

有没有一种方法可以在值发生变化时调用一次某个方法？我为 bindingHandlers.value 创建了调用此方法的包装器：

var update = bindingHandlers.value.update;

bindingHandlers.value.update = function(element, valueAccessor, allBindingAccessor, viewModel) {
    var newValue = ko.utils.unwrapObservable(valueAccessor());
    var elementValue = ko.selectExtensions.readValue(element);
    var valueHasChanged = (newValue != elementValue);

    update(element, valueAccessor, allBindingAccessor, viewModel);

    if (valueHasChanged) {
        myMethod();
    }
}

不幸的是，当我更改某个值时， myMethod 被调用两次，因为 dependencyObservable 也发生了更改。有什么想法吗？

原文

Is there a way to invoke one time some method on value changed? I created wrapper for bindingHandlers.value that invoke this method:

var update = bindingHandlers.value.update;

bindingHandlers.value.update = function(element, valueAccessor, allBindingAccessor, viewModel) {
    var newValue = ko.utils.unwrapObservable(valueAccessor());
    var elementValue = ko.selectExtensions.readValue(element);
    var valueHasChanged = (newValue != elementValue);

    update(element, valueAccessor, allBindingAccessor, viewModel);

    if (valueHasChanged) {
        myMethod();
    }
}

Unfortunatelly when I change some value myMethod is called two times becuase come dependencyObservable is also changed. Any ideas?

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

陌生 2024-12-23 10:31:22

如果您只想订阅更改的值，则可以订阅任何可观察的：

var viewModel = { property: ko.observable() };

viewModel.property.subscribe(function(newValue) {
    //do stuff
});

要订阅对象的所有属性，您可以执行以下操作：

function subscribeAll(viewModel) {
    for(var propertyName in viewModel) {
        if(viewModel[propertyName].subscribe === 'function') {
            viewModel[propertyName].subscribe(function(newValue) {
                //do stuff
            }
        }
    }
}

If you just want to subscribe to a value changed, you can subscribe to any observable:

var viewModel = { property: ko.observable() };

viewModel.property.subscribe(function(newValue) {
    //do stuff
});

To subscribe to all properties of an object you could do something like:

function subscribeAll(viewModel) {
    for(var propertyName in viewModel) {
        if(viewModel[propertyName].subscribe === 'function') {
            viewModel[propertyName].subscribe(function(newValue) {
                //do stuff
            }
        }
    }
}

回复收藏 0 原文

~没有更多了~