希望这对 knockout 大师来说是一个快速的过程......
我正在编写几个自定义绑定(bind)来帮助我在我正在处理的项目中使用自定义翻译引擎翻译 UI。
一种是翻译文本，另一种是翻译 HTML5 输入元素上的 'placeholder' 属性。
除了最后一个语句之外，这两个绑定(bind)都是相同的，其中一个更新元素中的文本，另一个更新属性值。
文本一个完美地工作，但占位符一个没有，我一直在寻找为什么的答案。
绑定(bind)代码如下:
译文装订
ko.bindingHandlers.translatedText = {
init: (element: HTMLElement, valueAccessor: Function, allBindings: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext) => {
// Get our custom binding values
var value = valueAccessor();
var associatedObservable = value.observable;
var translationToken = value.translationToken;
// Set up an event handler that will respond to events telling it when our translations have finished loading
// the custom binding will instantly update when a key matching it's translation ID is loaded into the
// local session store
window.addEventListener("TranslationsLoaded", (e) => {
//associatedObservable(" "); // Force an update on our observable, so that the update routine below is triggered
associatedObservable.valueHasMutated();
}, false);
},
update: (element: HTMLElement, valueAccessor: Function, allBindings: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext) => {
// Get our custom binding values
var value = valueAccessor();
var associatedObservable = value.observable;
var translationToken = value.translationToken;
// Ask local storage if we have a token by that name
var translatedText = utilityLib.getTranslatedString(translationToken);
// Check if our translated text is defined, if it's not then substitute it for a fixed string that will
// be seen in the UI (Whatever you put into the 'associatedObservable' at this point WILL appear in the element
if (undefined === translatedText || translatedText === "" || translatedText === null) {
if (sessionStorage["translations"] === undefined) {
// No translations have loaded yet, so we blank the text
translatedText = "";
} else {
// Translations have loaded, and the token is still not found
translatedText = "No Translation ID";
}
}
associatedObservable(translatedText);
ko.utils.setTextContent(element, associatedObservable());
}
} // End of translatedText binding
翻译后的占位符绑定(bind)
ko.bindingHandlers.translatedPlaceholder = {
// This one works pretty much the same way as the translated text binding, except for the final part where
// the translated text is inserted into the element.
init: (element: HTMLElement, valueAccessor: Function, allBindings: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext) => {
var value = valueAccessor();
var associatedObservable = value.observable;
var translationToken = value.translationToken;
window.addEventListener("TranslationsLoaded", (e) => {
debugger;
associatedObservable.valueHasMutated();
}, false);
},
update: (element: HTMLElement, valueAccessor: Function, allBindings: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext) => {
var value = valueAccessor();
var associatedObservable = value.observable;
var translationToken = value.translationToken;
var translatedText = utilityLib.getTranslatedString(translationToken);
debugger;
if (undefined === translatedText || translatedText === "" || translatedText === null) {
if (sessionStorage["translations"] === undefined) {
translatedText = "";
} else {
translatedText = "No Translation ID";
}
}
associatedObservable(translatedText);
element.setAttribute("placeholder", translatedText);
}
} // End of translatedPlaceholder binding
这个想法很简单，如果绑定(bind)运行并且翻译已经存在于 sessionStorage 中，那么我们拿起翻译后的字符串并将其插入与元素关联的可观察对象。
如果翻译已加载，但未找到翻译，则将“No Translation ID”插入到绑定(bind)到元素的 observable 中。
如果尚未加载翻译，请将一个空字符串插入 observable，然后等待事件“TranslationsLoaded”触发。引发此事件时，绑定(bind)到元素的 observable 会发生变化，导致发生更新，进而重新检查翻译，然后发现翻译已加载并因此采取相应措施。
然而.....
不管我多么努力，翻译的占位符绑定(bind)都不会触发它的更新。
我可以在调试器中清楚地看到，在两个绑定(bind)上都收到了事件，并且调用了 mutate 函数。
在翻译文本绑定(bind)上，我得到以下序列......
“初始化”->“更新”->“事件”->“变异”->“更新”
这正是我所期望的，它发生在绑定(bind)到该绑定(bind)的每个元素+可观察对象上。
在翻译的占位符上我得到
“初始化”->“更新”->“事件”->“变异”
但最终的更新永远不会发生。
结果，占位符的翻译字符串永远不会正确查找，具有相同代码的文本可以完美运行!
对于那些会问的人，我正在使用这样的绑定(bind):
<input type="text" class="form-control" data-bind="value: userName, translatedPlaceholder: { observable: namePlaceHolderText, translationToken: 'loginBoxNamePlaceholderText'}">
<span class="help-block" data-bind="translatedText: {observable: nameErrorText, translationToken: 'loginBoxUserNameEmptyValidationText'}"></span>
在 View 模型中，'observable' 参数只是普通的 ko.observable 保存字符串的变量。
干杯
肖蒂
最佳答案
我相信你有事件冒泡问题......尝试在你调用 valueHasMutated 之后放置一个'return true'，如下所示:
init: (element: HTMLElement, valueAccessor: Function, allBindings: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext) => {
var value = valueAccessor();
var associatedObservable = value.observable;
var translationToken = value.translationToken;
window.addEventListener("TranslationsLoaded", (e) => {
associatedObservable.valueHasMutated();
return true; // allow event to bubble
}, false);
},
话虽如此，我认为所有这些手动赛事对于 knockout 可以为您做的事情都是不合时宜的。你应该观察你的数据，绑定(bind)它，并让 knockout 为你做所有的内部事件......这就是它的作用。
一个建立在 user3297291 的 fiddle 上的例子:
ko.bindingHandlers.translatedPlaceholder = {
init: function(element, valueAccessor) {
var va = valueAccessor();
var obs = ko.utils.unwrapObservable(va.obs);
var placeholderStr = obs[va.key];
console.log(placeholderStr);
element.setAttribute("placeholder", placeholderStr);
},
update: function(element, valueAccessor) {
var va = valueAccessor();
var obs = ko.utils.unwrapObservable(va.obs);
var placeholderStr = obs[va.key];
console.log(placeholderStr);
element.setAttribute("placeholder", placeholderStr);
}
};
var vm = function() {
var self = this;
self.dictionary = ko.observable({
"placeholder": "Initial State"
});
self.switchTranslations = function() {
// Set the 'new' dictionary data:
self.dictionary({
"placeholder": "My Translated Placeholder"
});
};
}
ko.applyBindings(new vm());
fiddle :https://jsfiddle.net/brettwgreen/5pmmd0va/
关于javascript - Knockoutjs valueHasMutated 无法正常工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37412304/